Affected versions

• Firefox 94.0b3
• Firefox 95.0a1

Affected platforms

• Ubuntu 20.04
• Windows 10
• macOS 11.6.1

Steps to reproduce

1. Launch Firefox and access about:logins
2. Save 2 or 3 random credentials for https://www.twitter.com
3. Access Twitter and select Sign In

Expected result

• The autofill prompt is shown for the account part

Actual result

• The autofill is not shown at all

Regression range

• Will see for a regression, seems like the page was recently changed and that may be the cause

Additional notes

• The issue can be seen in the attachment.
• When entering the Sign in part, there will be a used history accounts, but if selected, will only reset the page.
• By entering an valid email account. the password part will be shown where the autofill will actually be available.

This is a duplicate of Bug 1733944, and the issue is indeed due to the login form layout that recently changed and as per Dimi, this is somewhat expected since: "We don't autofill the username field in the page because the username field is a formless username-only field, we don't support this now."