Unable to use newly created login in iOS app

I need to create an account for a newly installed iOS app. I opened the 1Password app and created a new login. I then returned to the app on the account creation screen (user name, password, confirm password), did a long press in the password field, selected autofill, password, then searched for my newly created login in 1Password. It's not found. If I return to the 1Password app, it's there. If I look in 1Password on my Mac, it's there. I can see it everywhere, except in the 1Password selection screen from the autofill.

To make matters worse, the vendor has no web-based version of the app, and they block pasting in the password field. 

Fully closing the app and 1Password didn't help.

How can I access newly created logins from within an iOS app?

Current versions of iOS and 1Password are the most recent available.