It always says, that the number is wrong, but it is right… Thank you!
Question
Problem with registration of Paper Pass
I see it, when I try to add a traveller to my trip.
OK, so that's on the website. Are you using the correct pass cover number? That's a capital letter “i” and 8 digits.
Also note that the Interrail website isn't the best place to book reservations. In fact, they can all be booked elsewhere, often cheaper. See this overview:
https://www.seat61.com/interrail-and-eurail-reservations.htm
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