New beta downloaded today. Now trying to launch 1P throws "The application “1Password 7.app” is not open anymore."
1Password Version: Not ProvidedExtension Version: Not ProvidedOS Version: Not ProvidedSync Type: Not Provided
This seems to be an issue, more so with macOS in general from what I have read. Others have experienced the same message, including while using Apple's own apps. A restart of your Mac will often help. It seems to happen when an app runs out of memory, possibly due to macOS rationing resources. If you have any high memory usage apps running, you might consider shutting some of them off if the problem continues.
There is a discussion on the Apple Communities though it is a bit dated at the moment. https://discussions.apple.com/thread/7465484
I would suggest contacting Apple directly if you continue to have trouble. Perhaps they can make a suggestion.