AP's in the same subnet as the physical topology (esa0, PHY, AP Registration checked).
APs were already registered with EWC (initially deployed with .ova 10.11), but after upgrade to 10.31.x APs won't register anymore.
APs have regular IPs, respond to ping and can be accessed via ssh;
# cget config global shows correct lastAcIp
esa0 responds to ping from AP.
Please advise.