Weird, I can upload animations fine. Have you done anything unusual with the animation, or is it just a standard roblox animator animation? If not, all I can think of is Roblox being down. I’ve had some troubles with packages, so it might be down/struggling.
Looked it up, 500 is an internal server error and 422 is an inappropriate name. If you keep getting 500, try restarting your router and studio, if you keep getting 422, just experiment with the names.