Think I sussed but partly by mistake. The secret seemed to be that it worked on a new Chrome tab opened AFTER I'd set up enpass. When I tried a login, I clicked on the extension icon and the usual Enpass filtered pop-up appeared so it seems to be working.
Still surprised this is still in beta though.
I've just received a new Chromebook. I've joined the beta programme and installed the chrome os enpass chrome extension. I've checked the "allow autofill on beta" (or similar) checkbox when the enpass extension first popped up however I don't know how to autofill a password. I click in a passweord field on a webpage but no enpass button pops up as it does on the android or MS Wwindows versions of the Chrome extension.
I'm surprised that chrome os support is still under a beta programme. Chromebooks are now mainstream especially given the pandemic has greatly increased chromebook shipments.
Trying the above out to see if I could live with a chromebook but it's not looking good. I've followed instructions to install enpass from the Google store but it says it's already installed and that'll be because I've it installed on my android phone. I can't see how to install it on this chromebook emulator/software installation. Thanks.