I've launched Caprine today casually (as I do every day) and only a blank Messenger window appears. Restarting the app (and Ubuntu) does not fix the issue...
Caprine 2.26.0
Electron 4.0.1
linux 4.18.0-13-generic
Locale: en-US
The issue is on the Messenger's side:

Thanks for the quick response. I guess we'll have to wait for FB to fix the issue. Cheers!
鈥nd it's back! Closing this issue. 馃檪
(though it seems their fix is propagating slowly, so it might take some time and/or a couple of refreshes to make it work)
Caprine works again. Thanks gentlemen, and have a great day! :D
Most helpful comment
(though it seems their fix is propagating slowly, so it might take some time and/or a couple of refreshes to make it work)