YouTube now blocks access if you try to use an adblocker.

This is another way Google is trying to push users to pay for their YouTube premium instead of using a free adblocker. Not everyone have run into this issue yet, but knowing Google it's not long.

Bypass

One way you can bypass this by using a frontend service like piped.video
You can make accounts on our piped page to keep your subscription feed.

If you wish to import your subscription feed go to piped.video/import and read how to.

Other instances can be found at https://github.com/TeamPiped/Piped/wiki/Instances

I also recommend using a tool like LibRedirect. This tool will send you to a YouTube frontend when you open a youTube link.
LibRedirect