Unless you said something like "I'd love to see you, but I don't have the energy to go out or make big plans", they might have thought the reason you weren't making plans with them was that you didn't want to see them.

An adage I really like is "never attribute to malice what can be equally well explained by stupidity". And then, never attribute to stupidity what can be equally well explained by miscommunication. They probably had no idea that what you needed was for people to put in that effort - they may have thought "well, she hasn't made plans with us, maybe she's bored with us?" They may have just not wanted to bother you.

I don't live in Austria, but I live in Germany, which I suppose has a similar property. Notice how in restaurants, the servers don't bother you unless you get their attention, while in America they're constantly hovering and asking "how is everything? everything fine?" I think Germans in general treat people's personal space as more sacrosanct, while Americans are very... attentive, maybe? The negative way would be to say Germans are aloof and Americans are nosey. Or maybe Germans are askers and Americans are guessers?

Either way, I think you're probably being too harsh on your Austrian friends. They'd probably have been more than happy to be the ones to make the effort - if they knew that's what you needed. And, not being telepathic and with a bit of a culture gap, that one small piece of effort to mention it sort of... ends up being something only you can do.