Whenever I try to cast Netflix to my Shield it just opens the shield's local Netflix app to the profile selection screen instead of playing the show I want. I talked to Netflix's support and they say the issue is Nvidia's (who according to support made the app). I'm in the process of talking with Nvidia's support, but they respond at a rate of 1 email per day, so I haven't gotten far on that front. The error prevents both normal casting and voice casting, which is really annoying. Anyone know of a solution?
I've not experienced this issue so don't have any definite fix to offer but we can at least make sure you go through the general troubleshooting steps for when android apps act weird. I'm going to assume you've rebooted both devices (shield and whatever you're casting from) but if not definitely try that first.
After that clear the data of the Netflix app and the Google Cast Receiver app on the Shield, and the Netflix app and Google Home app on your phone.
I'd also try casting from a different device like a friend's phone or a computer, just to eliminate possibilities. I'd be surprised if clearing the data on everything doesn't fix it though.