Just spotted an issue (which has a manual workaround) on the https://stockplanconnect.morganstanley.com website when logging in.
1Password populates the username, but webpage is set so that it physically changes the username entered, masking out all but the first 2 and the last 2 characters. So for example, when 1Password populates a username "mytestuser", the web page changes the name to "my******er". 1Password then populates the password field no problem, but of course by this stage the physical name is set by the web page to "my******er" which of course is not correct.
So for now the present workaround is to manually replace the username by typing or pasting it into the username field, after the password field has been populated. Doing this allows a successful log in.
1Password Version: Not Provided
Extension Version: 2.5.1
OS Version: Windows 11