Never rely on the Rail Planner app of interrail. It's often wrong or faulty, like here. Always trust on the operatoring company's planner, like here ÖBB. 

You can always add a train manually in the rail planner app. Scroll down in the planner page you screenshotted, at the bottom you'll see add a train manually. Click it, fill in the details (departure time and station, arrival time and station) and you're good to go, once added to your trip and pass. No need to stress about it, you have a valid pass and the reservation you need. 

Best not activate the travel day, just before you board your nighttrain. 

Hi,

 

I was just hoping for some assistance. I have booked a couchette cabin on the 9.27pm overnight train tomorrow (January 14th) to Vienna. (Attached train screenshot. 
I am now trying to add the train journey to my eurail app however it does not seem to exist in the app? (I have also attached screenshot)

Would someone possible know why this is? I am worried for if we get on the train with the seat reservation but the eurail pass can’t find the train.

thank you! 

 

Solution:

Tab the orange Filter button. 

Scroll down to the bottom.

Activate bike transport (I do use an other language version of the app, but it should say something that means just this).

Search again for your connection. Now it's shown.

(You did ask, why it's not shown: There's a later direct train at 23.27 that arrives in Zürich at the same time (8.20). So the app thinks it's not logical to leave earlier at 21.27. But with a night train it sometimes is.)

Kind regards, Hektor.