Tony I had a similar issue on Windows desktop app a few days ago - blank top bar, different font styles, and other layout issues. No idea why this corruption occurred, restarting and rebooting didn't help. To resolve it I uninstalled the app AND found where Heartbeat settings and cache where stored and manually deleted those. Then on reinstalling the app the display layout was corrected. The manual deletion of everything related to Heartbeat was essential, Heartbeat does not clean up after itself when removed and simply uninstall/reinstall the problem persisted.