Root Cause: HTTP400 – The size of the request headers is too long
TL;DR; Unable to create new workplace accounts in Windows 10. Root cause = ‘400. The size of the request headers is too long’ when sending OAUTH API requests to https://login.microsoftonline.com/common/oauth2/v2.0/authorize. Multiple instances of x-ms-DeviceCredential & x-ms-RefreshTokenCredential in Request Headers. How to fix?