It’s not uncommon to do it that way, by speaking to the staff on the train to buy the couchette.

No guarantees, but I don’t think you’ll have a problem with it being full. Especially if the reservations system is broken for everyone!

Yeah, just go to the train and try your luck. In worst case conductor might sell you his compartment I suppose… and now is so or so not main season, so unlikely that it will be full.

Alright thanks all, that's what I wanted to hear haha! I'll try and will keep this thread updated, so people know if that's doable or not

Last year this train was a terrible time keeper arriving in Plovdiv sometimes two hours late due to engineering work. We decided to travel back and pick up the train in Sofia so we were not waiting in the cold in Plovdiv! It was a very good decision on the night we travelled. You’ll also have a better chance of getting a place and Sofia will most likely have some reservations available. Our advice is pay for a sleeper last year it cost the equivalent of 30 euros for both of us. The sleepers are in my opinion the most comfortable in Europe but you’ll still have to get up in the middle of the night for passports . We arrived three hours late so had a very civilised sleep. Bring your own food!

Has anyone else tried this recently? I’ll be trying to get on at Plovdiv in the summer and worry it will be full!