The Subscriptions feed error message is resolved for almost everyone. If you're still seeing it, know that it will be fixed soon – thanks for your continued patience! You can follow along here for any additional updates: https://yt.be/help/CBxM https://twitter.com/TeamYouTube/status/1119013035580878848 …
Thanks for reaching out. Could you try uninstalling the app & reinstalling it after restarting the device to see if that makes any difference? Let us know.