Question: Buying C+ Seats on MCO-LHR
So i'm trying to buy some seats for my parents MCO-ATL-LHR and the flights I found only have Main cabin and Delta one as booking choices. The comfort + column on the booking screen says "Not Available" - when its clear that the chosen flights are configured with C+ seats.. What gives? Also I cant find the pay with miles button anymore.. eliminated/moved?
Flights are:
MCO-LHR: DL28/30
LHR-MCO: DL31/1848