Never book reservations through the Interrail/Euraik websites. The overview is unreliable and confusing, there are extra fees, etc.

Instead use the companies websites whenever possible. For this night train ÖBB website -> add Interrail/Eurail as a discount.

General guide: https://www.seat61.com/interrail-and-eurail-reservations.htm

According to the Nightjet website your night train is likely to be rerouted due to engineering works. Expect earlier departure and later arrival times. You'll be noticed.

Side note but feel free to check the Vienna - Bregenz service too. It has shiny new carriages and it is cheaper too!

Feel free to ask anything.

Next part of my question!! OK so ive been back onto the OBB website and entered that I have a first class interrail global pass and I’ve been able to book the train from Vienna to Zurich via Munich on the 19th september . However when it comes to seat reservations I’ve only been able to reserve seats from Munich to Zurich. The first leg from Vienna to Munich indicates £0.00 for seat reservations and doesn’t permit me to process anything. What does this mean? Are the seats all booked? Have they not been released yet? Will there be no seats free on the train? As I’m elderly I dont want to have to stand for 4 hours. The website doesn’t make it clear what the situation is. Help!

Vienna - Munich is not available yet. This is due to works in Germany that week. Expect different departure/arrival times. Check back in a week or two.

Btw is there a specific reason to go via Munich? Trains on this route are often packed and late (unfortunately...).

I'd rather travel on Vienna - Zurich direct. Not available yet either (due to the same works). These trains are likely to be redirected, 60-90 min longer travel time. Same thing: check back in a week or two when the works timetable should be published.

On ÖBB you can find this short notice:

Thanks for your help with this. I only chose the via munich route as the direct route wasn’t letting me book. I’ll check back in a couple of weeks and see how I get on.

I’ve messaged earlier about this but I’m not getting anywhere with booking. Just to recap i’m attempting to get from vienna to zurich on the 19th september. So far I’ve managed to get seat reservations from munich to zurich for a departure around 12.30.

However every website I try eg OBB DBahn etc are showing that all seats on all trains are fully booked. Anyone got any ideas???

Just wait a bit longer. Those trains can't sell out and nobody has been able to book yet.