Hi @I Thanks for posting in our Q&A.
Unfortunately you can only have one managed account on most of the apps on a single device. So if the user is a member of two tenants, or has two different accounts on a single tenant, they will not be able to set both accounts if they are both covered by an app protection policy. Have a look at: https://learn.microsoft.com/en-us/mem/intune/fundamentals/end-user-mam-apps-ios#manage-user-accounts-on-the-device
Allowing multiple accounts is one of the most requested features around MAM and you can submit your application at uservoice,. Hopefully it will be addressed by Microsoft in the near future.
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