Exactly the same here. The Enpass team seems to be overloaded by it's silly decision for a hard migration without fallback/delaying. I destroyed my installation on a business PC. Even after purging all I could find from the Enpass installation (files, registry, database) v6 doesn't start at all (just crashes). v5 was working but the browser plugin doesn't cooperate (even the old one I stored by myself: it doesn't connect to the running v5-main application). So my PC is unable to run Enpass v6 at all after upgrade.
edit: v5 now is also broken. Think, I broke it when I switched between v6 and v5 too often... Perfect time to change to another program.
Did you get it working?