@Daniel McQueen, Thanks for posting in Q&A. Windows 365 Business is a version of Windows 365 that is made specifically for use in smaller companies (up to 300 seats). It gives organizations an easy, streamlined way of providing Cloud PCs to their users. For the Windows 365 Business Cloud PC solutions, it supports for work account instead of personal account to sign in. Here are some links about Windows 265 for your reference:
https://www.microsoft.com/en-us/windows-365
https://www.microsoft.com/en-us/windows-365/faq
Please change to the work account used when the windows 365 cloud PC is created to sign in to see if it can work. However, if the work account is unable to sign in, you can open case to get help:
https://learn.microsoft.com/en-us/mem/get-support
Hope the above information can help.
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