An Office service that supports add-ins to interact with objects in Office client applications.
Hi. I have run into the same issue previously. Keeping the same scopes configured in the azure app registration in the manifest did the trick.
Corresponding Scope section should look like this
<Scopes>
<Scope>openid</Scope>
<Scope>profile</Scope>
<Scope>Mail.ReadWrite</Scope>
<Scope>Mail.Send</Scope>
<Scope>User.Read</Scope>
</Scopes>
I hope this is useful.