Download the log file of the SBS. It will list the listening port. It should be 1000 higher than the FS port. If not, there may be a port collision in your configuration. In the following case, it's 48671.
2020/02/15 08:28:08 INF 670504768 SBS-133 module_manager.cpp 759 cmdHandler_createModule : Creating module 'sbs' of class 'SessionBrowserServerMod' with params 'suAddr=example:49999 listenPort=48671 ring_db(host=example user=example password=example base=example)'
Attempt to make a TCP connection to see if the SBS is reachable from the outside.
telnet example.ryzom.dev 48671
Attempt to make a TCP connection locally, from the server itself, if it's not reachable from the outside.
telnet localhost 48671
If the TCP service is not available, the SBS service may not have been able to launch properly. Look for SQL errors in the log.
2020/02/15 08:28:08 WRN 670504768 SBS-133 mysql_wrapper.cpp 156 _connect : Error during connection to database 'username:database@hostname' :
2020/02/15 08:28:08 WRN 670504768 SBS-133 mysql_wrapper.cpp 157 _connect : Mysql_real_connect error :Lost connection to MySQL server at 'reading initial communication packet', system error: 107
This may indicate an authentication issue. If you're using host validation, check the SQL server logs for authentication failures.
FIXME: If SBS fails to connect to SQL this should show some warning in the status field on the admin panel!