So right now I am running the Android P Beta 3, and while I know it isn't released yet, I thought I would bring up this issue in case it is something on your side.
I can't seem to make autofilling work in the beta (at least not consistently). My test case is the Capital One app, which has always worked for autofilling (though I am noticing this behavior in other apps such as Chrome as well). The "Autofill with 1Password" dialog does show up, but when I click on my capital one entry, it just doesn't do anything. I have all of the filling settings turned on, and what is weirder is that when I switch to the keyboard, after selecting my login, the "Fill Username" and "Fill Password" buttons don't show up anymore.
1Password Version: 7.0.BETA-15
Extension Version: Not Provided
OS Version: Android P Beta 3
Sync Type: Dropbox