I'm experiencing this condition now after installing the latest Enpass release from the app store (6.3.1 (576) according to the About menu).
I tried closing and reopening Enpass and it prompted me to reauthenticate with iCloud (despite my having previously checked the "Stay logged in" option), but even after successful authentication, the synchronizing process just spins and spins and never completes. I'm experiencing this on two machines, a Mini and a Macbook Pro 15, both running 10.15.1. I'm able to browse my iCloud store to the Enpass directory without issue, so both computers are able to talk to iCloud successfully independent of Enpass.
Everything was working fine before I installed the most recent Enpass release, so I'm thinking the update must have broken something.