What does VBA Error 400 typically indicate, and what are its common causes?

VBA Error 400 signifies a 'Bad Request' error. It often arises when VBA attempts to interact with a service (like a website via XMLHTTP) that rejects the request due to malformed syntax, invalid data, or exceeding limitations (e.g., request size). Common causes include incorrect URLs, improperly formatted data being sent, exceeding API rate limits, or attempting actions the target server doesn't support.