IPv6 not working on clients

I recently noticed that IPv6 is not working on my clients. If I do wget -6 google.com on my PC, I get a timeout (I tried both Windows and Linux). When I do the same on my router, it works. Accessing Foris via IPv6 also works, if I use the router’s IPv6 address. I’m not sure when exactly it stopped working, but it did work at some point. I even tried a factory reset, that didn’t help. I’m using TurrisOS version 3.10.3. Does anyone have an idea on how I could debug this?