Hi everyone! I am trying to take a train at the 18th of July 2022 from Utrecht Centraal to WIEN HBF (Austria). One of the options is to take a train from Utrecht Centraal at 8:34, arriving at FRANKFURT(M) FLUGHAFEN FERNBF (Germany) at 11:49 and taking the train here at 12:01 to Wien Hbf.
Interrail says that this is a popular train, but that a reservation for a seat is not necessary. I have tried to book a seat for 2 people at different timeslots and on different websites (bahn.com, interrail etc.) for a while. First, it looks like I am able to reserve a seat, but when trying to purchase the reservation it always tells me that I have to find an alternative connection.
Now my question is, can I still take the above train without a reservation, and for example, stand in the train. Since it no longer seems possible to reserve a seat.