I recently did a complete reset of my iPad. After re-installing the app, I went to restore purchases. When I press the button, it says "Failed to restore purchases. There are no purchases associated with your Apple ID. You may have made the original purchase with a different Apple ID or possibly with a family member's account."
I still have the functionality on my iPhone, so I know have purchased the option. The only other thing that comes to mind is that I recently changed the email address associated with my Apple ID, but it's the same account as before.
1Password Version: 7.0.6
Extension Version: Not Provided
OS Version: iOS 11.3.1
Sync Type: iCloud