Dark mode not retained on re-instal

I made a donation which released dark mode.
Then re-installed Linux on my laptop, and also Cryptomator.
However, the original donation key does not work.
Does this mean I have to donate every time I re-install Cryptomator on my computer?

Thanks, Ken

No, you absolutely can re-use the donation key. Make sure that there aren’t any copy/paste errors (no whitespaces/linebreaks etc.)

Well I’ve tried different ways to paste this in, trying to ensure the absence of hidden characters such as linebreaks, etc. Still won’t accept it.