When you active your pass and choose a start date, that date is automatically made a travel day, even if you don't add a journey to the pass that day.

This is why the experienced travellers say that you should never activate your pass until just before boarding the first train of your travel. You never know if your travel plans will change if you activate your pass in advance and you risk loosing a travel day as you just did.

What night train couldn't you use your Global Pass on?

Thanks for the reply

All Nightjet trains are included so I'm curious where you got the idea that this wouldn’t be the case.