I have been using Join for quite a while now, and I occasionally (and currently) have this problem. I'll get a text message on my phone (Galaxy S8), I'll get the notification in Chrome (on Windows 10) and for a couple of seconds, the message will be visible in the join window, but then the notification will disappear. I have a bunch of messages from previous days available, but nothing from today. Refreshing the Join window does nothing. Going to diagnostics and running the test does nothing. I've closed Chrome, rebooted and removed and reinstalled the Join extension and nothing works.