I was getting ads in two installments, one of 13/14 another of 11 or so. you may also have the same problem.
I stopped watching ads and waited for a day. now getting all 25 at a go.
but the ad loading/refresh problem still persists. after every 4 it's showing no ad available but if I click on home and then come back, then there are ads available (or sometimes I've to disconnect the net and again reconnect).