jsaathof

Sadly this worked only once. But I have found the issue. I had turned on the option in Prefrences -> Browser -> This system-wide hotkey will launch Enpass helper. After turning it off the helper started working again.

I have downgraded to Firefox 62.0.3 and it works again. I guess this is an incompatibility in the latest Firefox.

It is probably an incompatibility with Firefox 63.0.1 because I have the same issue on MacOS X 10.14.