Hi ,
Please check these senarios...
RFC - Means JCO and SM59...
SSO...
Servenode Satus...
1. RFC created should have checked the radio button 'registered server program' in SM59.
2. check if some restart or instance is down on Java instance.
3. Check in SMGW if program is sapfallback visible here. Goto-> Logged On Clients, here you should be able to see sapfallback entry.
BR,
Prabhakar