Perhaps you are running into ...

Events (and opponents) are set and announced 2 days before event start.

[So, for example, expel order mates from order before Sunday 0h00z or they will be included in your order size for OvO starting Tuesday 0h00z.]

See if your experience above repeats itself for inter-k events, going forwards.

The event has now started,  showing in active events, still no opponent, and not allowed to add points to it ,  can someone from plarium explain what is happening here please 

See and answer the prior.

When the events start is not important, what is important is when they are announced. (2 days prior.)

Reply back if you see the same for the coming KvK or the next OvO.

When event started we met all requirements,  the event OVO stayed in place as active during the time it ran,  but no opponent,  our whole kingdom was the same,  and we have no KVK this week either, didnt even show up in events 

Something similar happened to us.  We switched  orders in the same kingdom  before ovo was announced.  But we could not particpate in ovo or kvk  for a week.