The AMB JS client gets disconnected for long enough for a chat session to go away. When the client re-connects to the browser (also mobile) it fails to re-subscribe to the channels.
Steps to Reproduce
1. Open two windows with different users and start a chat.
2. Disconnect the internet for more than 30 seconds.
3. Reconnect the internet.
4. Try resuming the chat between the two users.
Notice the second user does not get the message you attempt to send.
This problem has been fixed. If you are able to upgrade, review the Fixed In section to determine the latest version with a permanent fix your instance can be upgraded to.
The only workaround is to refresh the page.
Related Problem: PRB1349642