See https://github.com/brave/browser-laptop/pull/14362
(Placeholder. Have not reproduced).
Users report that CAPTCHA does not work correctly with some Windows 10 UI/font scaling options. Apparently when Windows is set up for high-res monitors it does not work because of use of absolute x/y coordinates.
I believe a few of us ran into this with VM's but we figured it was a VM specific issue. Example of the issue occurring in the VM:

Unfortunately I didn't end up reporting this as everyone that I asked said it was working fine on Win so assumed it's probably a VM issue :/
Confirming that this is indeed due to scaling. If you reduce device scaling to 100%, it should work.
@srirambv @LaurenWags @btlechowski @GeetaSarvadnya Even though this was fixed for the scaling issue on Win, we should double check and make sure it still works as expected on all three platforms, hence adding this issue to all three manual passes.
Verified with macOS 10.12.6 using
Verified on Ubuntu 17.10 x64
Verified on Windows 10 x64 using