Similar experience here, just redeemed points for a 12-month Calm subscription and did not receive an email for it. I tried the code that was presented on the Rewards website after redemption and got an error message that the code is invalid and tha...
Same exact problem here with Nvidia Shield, blank screen with top row links only, expired token message, channel not part of your subscription message. The only thing that works sometimes is Force Stop in app settings, or device reboot.