For what it's worth I'm having this same issue with Quickbooks Online and it seems to be caused by a recent change in the "modern design" of the web app's login/auth page and may have something to do with a failure to check or send out MFA codes via SMS messages because that also failed.
I'm on MacOS Sonoma and using Firefox and Waterfox when encountering this error. I've tried turning off all content-blockers but it's still not working.
My advice to anyone who gets this web browser error 'Something's not right. Try Again.' is use a different browser. I'm on Safari now and it works. This is a bit frustrating Intuit lists Firefox as a supported browser and it clearly does not work.
