I downloaded the app on your website, so I have access to some extra settings. I enable "include beta channel" and click "Check now", it says "You are up to date".
After closing the settings window and opening it again Include beta builds become unchecked automatically.
I tried to quit the app completely (control + option + command + q), downloaded the installer and reinstall the app. It didn't work. Tried twice.
My current setup:
1Password Version: 7.2.1
Extension Version: Not Provided
OS Version: Not Provided
Sync Type: Not Provided