[FWA510] Router still running, but web interface not reachable anymore

A few weeks ago I restarted my FWA510 because the web interface was not reachable anymore. The system just runs fine, It is getting every night a new ip address and I was able to login through SSH though, but couldn't do al lot because I can't find any documentation about the different commands or to restart the web interface.

After the restart the web interface was reachable again, but now it isn't anymore. What is going wrong here? The FWA510 runs in bridge mode.