MS 365 (Office) subscription not recognized by Microsoft

I've subscribed to Microsoft 365 (premium) on my iPhone and am billed annually, but my subscription is not recognized by Microsoft: when I try to "activate" it on any of my devices through any of MS applications, nothing is found. I'm using the email address associated with my iCloud account, which is also used for a MS365 account, but the MS365 account shows no transaction or subscription associated with the account, while I can see the subscription on my AppStore and iCould account on all my devices. Any ideas how to resolve?