NewPipe still working on my side and on their GitHub page there isn't any new Issue related to be broken again.
However, YouTube is doing a lot of AB testing these months... Trying to kill alternatives. Keep an eye on their GitHub.
Meanwhile, try to narrow down the issue:
- Try to log what's happening in the backend with ADB.
- Log your DNS records with something like rethinkDNS or PCAPdroid
- Check your Firewall rules on your phone
- Clear cache and data -> reboot
- Try to reinstall your app
- ...
If you're talking about self-hosted piped instance... Yeah they are a bit broken right now.