These trains run under a special regime-as TrenItalia did not want to run any treni OUT of the boot of Italy and are since done by DB and OeBB only-to have them run they needed more income and hence since then all passholders are now charged 10€ extra (or maybe a little more on the train-conductor will catch you)-IF done in DE or AT at counter, includes a REServ (which is optional as such-not very advisable in hi-summer). THat is what this means: pay extra. As has also been told here a few thousand times now.

Hello, I want to  make a seat reservation for this journey, but  this message show up. I’ve already read some things about this message in this forum but I really don’t understand what does it mean. Can someone explain what does that mean? And what are the solutions ?

 

you used the seat only option on oebb.at that is not the correct way :/

You have to add the Discount Interrail/Eurail and click then on Single / Oneway / Daytickets.