By default, Microsoft 365 GCC High environments are configured to prevent the use of mobile add-ins and will prevent these from being loaded on a device even when deployed from the Microsoft 365 Integrated Apps portal.
On Android devices, the add-ins option is not listed under the settings menu. On iOS devices, opening add-ins reports "This account does not support Add-ins"
To resolve this, the Microsoft 365 tenant must be modified through Exchange Online Powershell to allow the use of Outlook Mobile add-ins.
Connect to Exchange Online: and log in with a Global Administrator account:
Connect-ExchangeOnline
When connected, use the following command to disable add-ins on mobile devices:
Set-OrganizationConfig -OutlookMobileGCCRestrictionsEnabled $false
You can check this setting using the following command:
Get-OrganizationConfig | fl OutlookMobileGCCRestrictionsEnabled
Which will return the following when disabled:
