Some time ago Google made some changes to age verification, and now you can't watch age restricted videos without logging in, which means you can't watch them using NewPipe. It also means you can't watch them without handing over your phone number to Google, because it seems it's no longer possible to create a YT account without a phone number.
This whole thing makes NewPipe a lot less useful than it used to be.
This whole thing makes NewPipe a lot less useful than it used to be.