There appears to be some kind of bug or problem with your login screen that causes the CAPTCHA to get triggered far more often than it should, including in multiple situations where it shouldn't be possible to trigger a CAPTCHA call at all.

I have a screen recording of some testing I did, which I already provided to your support team (it is too big to attach here). Using the SSO Login page, I tested three "subdomains", all of which I know would not actually work for SSO (and should presumably throw an immediate error)

After entering each of these and pressing "Log in", I was prompted with a CAPTCHA each time. This makes no sense, since especially for the first one there is no call that should be getting made; it should just error out since the field is empty.

On each of these, if I actually complete the CAPTCHA, the page simply refreshes, with no error showing. On one test, I hit "login" with the field empty, then had to go through a painfully long CAPTCHA (I believe it was at least 12 separate "select the car / crosswalk / etc" windows), only for the page to refresh and be back at the start with not even an error message. Hitting login again prompted for a second round of CAPTCHAs, with no memory or indication that I had just completed one.

Something appears to be wrong with the login / CAPTCHA / verification flow because I am assuming this is not how this is supposed to work.