If you get this error, it normally means that there's been a disruption in your connection, and you can normally fix it by disconnecting and reconnecting.
Check your internet connection
Before you start, it's always worth double-checking that your internet connection is working, by opening a website and clicking links. If you're not connecting to a website, you may need to contact your IT team.
Disconnect the RemoteApp
Once you're happy that your internet connection is working, you can disconnect your RemoteApp.
In the Windows notification bar, right-click RemoteApp and Desktop Connections.
Click Disconnect.
After you've done this, you can reconnect as normal.