I have the exact same issue as Michiel, as well as having done basically the exact same steps to resolve the issue. According to the debug tools for the extension, I am getting repeated messages about failure to connect via the websocket:
I've also gone ahead and emailed the betabugs@enpass address, but posting here to get more visibility. I also noted that in this forum that there is another thread about the extension not working for Mac originally posted in September, but now has a couple of other users posting within the last week regarding issues again. It appears that with the latest push of the browser extension for enpass that it broke connectivity.