This also occurs to me on Pixel 7 Pro. Everything worked find on older Pixel 3. Have double-checked/compares all settings between the 2 phones and they match.
Using Swiftkey keybard.
(1) At times, tapping in username field will show the Autofill button at top of keyboard. Selecting autofill and the appropriate account it will only fill in username field. Leaves passoword field blank. Tapping in password field will just show keyboard with no Autofill button at top of keyboard.
(2) Other times I tap in the username or password field and get a pop-up on the field for Autofill with Enpass. Not sure why the different in functionality.
But mostly item (1) is what occurs.
Also, for the ones that do work, when I link the app to the enpass entry, returning to app and login again displays the associated enpass entry and a whole bunch of others as well that should not be associated with the particular app. Again, this did not occur on Pixel 3, just now the Pixel 7.
In the apps that Enpass is not working I have tested Bitwarden and Bitwarden is working as expected.