I have 1Password Version 6.8.8 (688001), syncing through Dropbox. I updated to Mojave and now I'm getting regular notifications from 1Password Mini:
Clicking on "update preferences" in the notification doesn't do anything, so I went to the Preferences menu within 1Password and looked at Sync. It's set up to sync through Dropbox, as before, and shows the last sync happened an hour ago. Not sure what else to do here to get syncing back. I have the latest version of the Dropbox app (60.4.107).
1Password Version: 6.8.8
Extension Version: Not Provided
OS Version: macOS Mojave 10.14
Sync Type: Dropbox