There was a problem connecting to the session

When connecting to FastX, the initial connection succeeds, but when you try to connect to a session, you receive the error.  “There was a problem connecting to the session”

Checking the details of the logs can provide more information.  Here are several common causes

1. SSH port forwarding is disabled.
   In this case, the connection log will have a message like this:
   Opening connection to 127.0.0.1:41120 for forwarding from 127.0.0.1:60178

   Forwarded connection refused by server: Administratively prohibited [open failed]
   This can be caused by having this line in /etc/ssh/sshd_config on the server:
   AllowTcpForwarding no

2. Session has died. (Xorg process has failed.)
   In this case, the connection log will have a message like this

   Opening connection to 127.0.0.1:41121 for forwarding from 127.0.0.1:60225

   Forwarded connection refused by server: Connect failed [Connection refused]
   Another possible log entry, instead of the “refused” error, is something like this:
   Forwarded port closed due to local error: Network error: Software caused connection abort

3. Windows Firewall is blocking localhost connections, or localhost is returning wrong IP address.
   In this case, the connection log will not have the “Opening connection to 127.0.0.1:…” message.