It is possible that the website spreads the user name and password across two pages and that Firefox isn't able to determine the username when saving the login. You can edit the username field in Lockwise and fill the corresponding username.

• https://support.mozilla.org/en-US/kb/password-manager-remember-delete-edit-logins

Thanks for this. I've used the edit to add one of the missing names (should have been obvious to me, but I've only just become aware of Lockwise - had to use it because of the annoying "update stored login" option.

I'm a bit confused about the rationale: -Are there any logical reasons why a website would spread username and password across two pages? For mine, it doesn't seem to be caused by number of characters -How come that in Lockwise some of the usernames aren't there, but all the passwords are?

Another issue is that some logins have duplicate entries in the list, one showing the username and the other not, but both with the same (correct) password.

As you've solved my original query, I don't want to waste your time, so I would be grateful if you would point me towards any other relevant support pages.

Firefox can recognize a password field because that has a type="password" attribute and that triggers the dialog to save the login if you submit the form. Firefox looks for an input field with type="text" further up in the DOM and apparently Firefox isn't able to find an input field with the username, so that is left cleared.