@Dave Coulson Thanks for posting in our Q&A. From your desription, did you mean that you want to reset the admin account's password in Microsoft 365 admin center?
If yes, this issue is not related to windows 365. It is related to Microsoft 365. Based on my research, the following article shows some information about resetting passwords:
https://learn.microsoft.com/en-us/microsoft-365/admin/add-users/reset-passwords?view=o365-worldwide#reset-my-admin-password
Hope it will help.
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