Hi Michal.
I think I saw this yesterday as well. New to me in V13 is the ability to use hostfiles to define servers (I'm coming from 12.1 - not sure when this came in or if it's new with V13). So far I haven't found any documentation on it but if it gets me out of multicast discovery ****, I want to use it. Anyways, I too had the 'no active servers', so playing around I clicked 'switch to host files' and manually defined the servers, then clicked it back to auto discovery and they were there.
HTH,
Rob