I have not been able to find a result for this on TurboTax, but I did find this response on Google.
A 400 Bad Request Error occurs when a request sent to the website server is incorrect or corrupt, and the server receiving the request can’t understand it. Occasionally, the problem is on the website itself, and there’s not much you can do about that. But most of the time, the problem is one you might be able to solve—maybe you typed the address wrong, or maybe your browser cache is causing problems. Here are some solutions you can try.
My experience with other programs has been to clear browser history and cache. That is my next attempt at resolving this as I am going through it quite a bit lately. Fingers crossed.
