Greasy Fork

Script works fine if you uncomment the code thoughtfully left by the author:
//document.querySelector("input[value='Verify you are human']")?.click();
document.querySelector('#challenge-stage')?.querySelector('input[type="checkbox"]')?.click();

To make the script work correctly with the new changes in the CloudFlare captcha, you just need to tweak the code a bit:
setInterval(function(){
document.querySelector('#blYgG5')?.querySelector('input[type="checkbox"]')?.click();
document.querySelector('.ctp-checkbox-label')?.click();
},3000);

What you need to do to make it work again It auto clicks but it says failed

CloudFlare captcha changed the code again, so these tweaks are needed:
setInterval(function(){
document.querySelector('#qrVk5')?.querySelector('input[type="checkbox"]')?.click();
document.querySelector('.ctp-checkbox-label')?.click();
},3000);

Tried the Streampunk mods and still doesn't work. Gone back to my PTFB workaround instead which always works to automated a virtual click in the right place, until a reliable solution is found.
https://www.portablefreeware.com/index.php?id=1220

Don't see new changes from Cloudflare, everything works as usual.
Maybe you have some special site or some other extension or script is preventing this userscript from working properly.

I should have been a bit more detailed. The script works in so much as it places the check mark in the box well enough, but what doesn't happen is Cloudflare accepting it as genuine. After the script places the checkmark, the screen just rolls around and around and then you get the message "It's taking longer than normal to process your request" and then it reloads in an endless loop. It appears that Cloudflare can determine the difference between a script placed checkmark and a real one placed with the mouse, and rejects the script placed one. Using PTFB to simulate a virtual mouse click in the right coordinates on the screen instead, works everytime.

https://chromewebstore.google.com/detail/dknlfmjaanfblgfdfebhijalfmhmjjjo
cloudflare free

https://chromewebstore.google.com/detail/dknlfmjaanfblgfdfebhijalfmhmjjjo
cloudflare free

Wow. That is truly fantastic. Thanks very much!

The script works in so much as it places the check mark in the box well enough, but what doesn't happen is Cloudflare accepting it as genuine. After the script places the checkmark, the screen just rolls around and around and then you get the message "It's taking longer than normal to process your request" and then it reloads in an endless loop. It appears that Cloudflare can determine the difference between a script placed checkmark and a real one placed with the mouse, and rejects the script placed one.

AFAICS the beauty of this userscript is that it completely simulates a mouse click using two consecutive clicks on Cloudflare triggers.
Endless loop and captcha reload can also occur with a manual mouse click, when Cloudflare doubts that your IP is clean enough, has suspicious browser settings, fake useragent and many other factors that we can only guess about.

Meanwhile, CloudFlare captcha changed the code again, so the new code looks like this:
setInterval(function(){
document.querySelector('#kNIq7')?.querySelector('input[type="checkbox"]')?.click();
document.querySelector('.ctp-checkbox-label')?.click();
},3000);

Having previously tried Autopass Cloudflare CAPTCHA which absolutely DOES NOT WORK and has been abandones by its developer, the failure symptom of Cloudflare Challenge is exactly the same. It has been assumed that the cause of this in Autopass Cloudflare was the lack of a delay in responding to the checkbox. ie. it was reacting way too fast which would be impossible for a human to replicate, so would be very easy to detect by Cloudflare and hence, reject. This is only supposition on my part however as I'm not clever enough to know exactly what the script is doing.

May I presume the 3000 number at the end of the script is the response delay in ms? Can this number be tweaked manually to test whether making it longer (for slower internet connections for example) might make a difference? As I said, I'm not a programmer, so do not possess the inate ability to know what the script is doing.

For reference, I'm on only a 25/10Mbps connection, which is the fastest I can get due to infrastructure limitations in my country, so web pages do not load instantaneously in the blink of an eye, like they do everywhere else.

Just tried tweaking the response delay time using the built-in option in the browser extension and making it 2000 or 3000 from the default 1000 made no difference. Cloudflare rejects the checkbox inserted by the extension and it just goes into an endless loop. I've switched off the Cloudflare Turnstile for now and will just use PTFB v1.06.3 instead for that one which is 100% reliable always. I run PTFB constantly as a TSR anyway for other annoyances, so it's no bother. Amazing how freeware from 2001 still has a brilliant use 23 years later!

Well, it's always good to find a solution that works for you.
Fixed userscript code to make it less dependent on weekly changes rolled out by Cloudflare:
setInterval(function(){
document.querySelector('div[id]')?.querySelector('input[type="checkbox"]')?.click();
document.querySelector('.ctp-checkbox-label')?.click();
},3000);

Interestingly, the Captcha on a file sharing website called Filespace.com looks exactly the same as the Cloudflare Turnstile, and the script works perfectly there first time.

use PTFB v1.06.3

Could you explain how to do this? When I try, it only recognizes the Windows forms and the buttons within them. If possible, please share your settings.

use PTFB v1.06.3

Could you explain how to do this? When I try, it only recognizes the Windows forms and the buttons within them. If possible, please share your settings.

You press and hold both left and right mouse buttons together and while holding them pressed, move the mouse to where you want a virtual click to be made. Then release the buttons and PTFB will if you want a virtual click to be made at the X-Y coordinates chosen on the screen. Obviously this only works as long as the checkbox always appears in the same location on the screen, which requires that you do not have your browser windowed and moved around the screen like a tile, otherwise the X-Y coorindate will change and then the click will not happen where you need it to.

From the PTFB documentation:

When PTFB doesn't acknowledge a button

Sometimes, PTFB may not acknowledge the target button - the finger does not become highlighted. This is often because the button is either highly customised, or does not exist as a true button control. To help deal with at least some these cases, PTFB 1.06 has a facility for overriding the normal button recognition rules.

To use this facility, hold down both the left and the right mouse buttons as you drag the finger cursor. You'll notice that the finger appears highlighted all the time, and PTFB's main window displays the current mouse coordinates. When the cursor is over the target button, be sure to release the left mouse button first. At this point, if PTFB still can't recognise the button it will ask you to confirm that you want to add a hitlist entry:

If you respond with "Yes", then a new hitlist entry will be created, but the target button will be described by a mouse position rather than by a button name. When PTFB next sees the dialog, it will apply all the validation tests described in the following section "Changing Settings for a Hitlist Entry". If the dialog passes, PTFB will simulate a mouse click at the button location. Please note that there's no guarantee that the dialog will react as though the button had really been pressed, but the technique does allow PTFB to work for a much wider range of dialogs.