This has also been happening for me on Mac for several months. Enpass suddenly forgot that I had ever registered and began running in trial mode. Every update I try to reactivate and every update it says "Could not connect to the server." on the activation modal. I'm currently running 6.12.2 (2560) from the Mac App Store. I tried installing little snitch to see what connection failed, and nothing at all was captured. As if Enpass didn't try any network connection at all before failing.