Solution:
Log into your Microsoft account and keep it open in another window, close Excel, and open Excel, Help is working. Pain in the backside. Thanks, Microsoft NOT.
Thanks. This led me to figure out how to get Help to work on my system. I have a Microsoft account (a.k.a., personal/consumer account) and a Work or School account (a.k.a., business/Azure AD/Microsoft Entra account). The Microsoft account is for my personal OneDrive and doesn't have an Office 365 subscription while the Work or School account does have an Office 365 license assigned to it. I was working on an Excel file stored locally on my PC when I was getting the error. After reading your solution, I clicked on the dropdown at the top of Excel and switched to my Work or School account, with the same file still open, and Help started working. I switched back to the Microsoft account and Help immediately stopped working again. So, even though everything else in Excel works with my personal Microsoft account selected, Help, as well as Contact Support, Show Training, and What's New, only work when my Work or School account is selected.