Hey Tenno! We are aware of this issue. We do not have a timeline for a fix, but we are investigating.
Could you try relinking your Warframe account to your Twitch account and see if the error still persists.
This thread was added on January 17, 2020, with posts from [DE]Saske.
Hey Tenno! The "Bad Request" popup should be fixed. We are working with Twitch on a solution for the missing rewards.