I had a designer review my site and their first note was that the 1password shortcut does not work on my Log In popup to automatically fill in their user name and password.
I investigated this a while back. To make them detectable by 1password (or Safari) the id of the input needs to have a unique identifier. That did it for me.
By the way, the standard that 1password follow is Apple’s. So I’m guessing if you have an Apple device, it should also detect it and suggest a password.