Tunnel connection is not working in hub 7.97
There might be some specific cipher specific error in hub log.
In tunnel server log :
hub: CORE server cipher=LOW:!ADH
hub: Error setting cipher list (no valid ciphers)
hub:  error: SSL routines:SSL_CTX_set_cipher_list:no cipher match
hub:  error: SSL routines:SSL3_GET_CLIENT_HELLO:no shared cipher
hub 7.97 is running in either side of tunnel server or tunnel client.
Tunnel server is using "Low" level security setting.
The problem is fixed in hub 9.10, however workaround is available as follows.
Please change [Security Setting] level from "Low" to something else.
This setting exists in tunnel server side hub.
The problem is not happening if you are using "None", "Medium", "High" or custom cipher such as "RC4-SHA"
NOTE. You don't need to re-create new tunnel certificates along with the [Security Setting] change.