Hey!
Which train are you trying to book? There are up to 3 nighttrains to Bucuresti.
The 15.10 definitely does NOT have sleeper, only couchette (4/6) or seat.

I’m trying to book the train NT 473 leaving from Budapest at 19:10

Where did you try to book?

MAV?=the hungar railways?

Some more clever systems show NO real sleeper if they are all already taken-and somewhere I read that due to works on 1 of the 2 lines linking HU-RO, this summer, many trains are cancelled=more people have to use the few trains remaining, so if its for not too far away this is well possible.

Also specific railfans forums tell that there are again ´probs´ with some sleepercars and they cannot be put in all train every day (or moreor less the same as this).

Can you improvise or does it all really have to be exact as you wanted it before trying and also on the days in a careful put scheme? Passes are meant for spontaneous and sometimes unexpected travels-not really for those who cannot live with things not going as they have though out.

I’m having a similar issue - interrail is showing me prices for sleepers and letting me put them in the cart, then giving an error and saying they’re not available after all. I tried the Hungarian and Romanian train companies; the sleeper tickets are available from CFR, but there’s no option for seat/reservation only, just the full ticket with reservation.