When would you like your travel ? Night trains are very popular and can sell out weeks in advance, especially this one. Most of the summer is sold out. As a note : there's always more availability from Basel.

Check and book on nightjet.com (no booking fee), the operator's website.

However seating carriages on this train do not require seat reservations, you can simply board. But the carriage will be fully lit and frankly you won't be able to sleep (not recommended).

If you let us know your travel date, we'll gladly help.

Planned trip will happen in the beginning of August

I checked the tickets to this train a few weeks ago already, and already then those were unavailable

I don't think I'm able to book (interrail prized) ticket in nightjet.com 

There is no difference between regular ticket and interrail availability on nightjet trains.

To book on nightjet.com or oebb.at you need to add interrail as discount for each passenger and search for tickets NOT seat only.

That's not a date...

As said: also check availability from Basel. If you use nightjet.com, then you can't use the wrong option that causes "ticket not available”.

It is totally possible that it is sold out. I've booked Amsterdam - Zurich in February for August and it was the last couchette available.

But as said, if you want precise advice, give us the travel date please