OACI-related failed task or billing order contains the following output:
Subscription limit for VE number exceeded
This issue is reported to the OA maintenance team as CCU-11508: "Unable to reschedule failed VPS subscription if VE was not created".
CCU-11508: is fixed in OA 6.0 update 6.
It is also fixed in OAP 7.0 as CCU-11529.