Sorry to hear that rhm! Folding bikes typically have very short chainstays which was most likely the issue. I've also had issues installing the Chainglider onto a mountain bike frame that had particularly short chainstays also. There is nothing in Hebie's specs that I found that defines what length chainstays it fits but I would not recommend it for anything shorter than 42cm and even then, longer is better.
I suppose in Germany most bikes have a relaxed geometry and aren't "performance" oriented like they are here in the US so this is not so much of an issue for them