"New Login" does nothing on a Naples MUG website form

The membership portion of the Naples (FL) MacFriends User Group (NMUG) website is hosted on a FileMaker database.

I'd like to use 1Password to fill in member forms. When 1Password didn't offer to save a 2-field login form, I attempted to manually save a "New Login", but nothing happens, i.e., no new entry & no error message. I suspect this is due to FlieMaker's web forms differing from conventional forms that 1Password can recognize and control.

Here's an example of a simple NMUG 2-field login form: https://naplesmug.com/html-for-update-3.htm

Note: That published HTML page redirects to the actual login form on a FileMaker hosting service.

Is there any way to coax 1Password into supporting this form (and others like it)?

-- Ward

P.S. Something strange is happening at the mcservices.com website. The form I saw before opening this topic looks like this:

joyofmacs.com/share/NMUG1.png

Now I see this (which 1Password recognizes as a login form):

joyofmacs.com/share/NMUG2.png

1Password Version: 7.9.2
Extension Version: 7.9.2
OS Version: macOS 10.15.7