Call to getUserIdentityTokenAsync() returning a nu

Question

We have an add-in in production where, for certain users, the call to getUserIdentityTokenAsync() fails and returns a null token.

The response is

"Status" = "failed", 
"Error" = {message: "An internal error has occurred", name: "Internal Error"}

Would anyone know what could cause this type of failure? Certain users always get the error, and we have never seen the error locally or during development.

It seems to happen only for desktop Outlook users. We have not seen any errors for users when using the add-in via the browser.

Answer 1

I am updating the answer based on a response from the Outlook Add-ins Team in the comments.

In MSI versions: 16.0.4540.1000 to 16.0.4585.1000 against Exchange 2013, GetUserIdentityToken did not work. In MSI versions before, 16.0.4540.1000 / 15.0.4931.1000 and C2R versions before 16.0.7813.1000 - calling GetUserIdentityTokenAsync along with MakeEwsRequestAsync would cause a failure

In my case, most of the users experiencing the problems had the client version numbers posted above. Upgrading their outlook version solved the issue.