BM3.8.5 on NW6.5.6

since today noon about time from the 21st VPN C2S client the people
out there get this error when logging in (IKE or NAT-IKE).

the client hangs quite a while at the negotiation part "Authenticating and .."

An error war reported by the ike application
Server not configured to allow these many clients

Where to configure this value? In the C2S Definition in iManager I cannot
find anything to configure a limit for the allowed number of VPN clients.

Looks like I miss something very basic.. :-//

Any suggestions appreciated,

regards, Rudi.