Are you local or remote to the AF Server? What do the AF Server logs say in the Event Viewer of the AF server itself? Is the AF Application service actually running? I see you have active SRP so if this is urgent for you then I would suggest calling into tech support to get someone to take a look at this right away.
Hi Kai Wisser
If you are still facing issue from client side, then I would request you to do a telnet from client.
telnet AFSERVERNAME PORTNUMBER. Looks like AF service is not available and would request you to check AF service logs on AF server.