Hi @Atonkin89
When the Last name, First name is passed to the Search users..

It correctly shows up both the email as well as the UPN Id.

Couple of things to check:
- As a sample test, pass a valid email address as the UPN to the "Search users" or "Get user profile" and after running the flow in the output check for the format of the DisplayName parameter.

In my case it is Last Name, First Name. And if I pass vice versa ie; First Name, Last Name it does not work.
Check how is it in your case. For eg; if it is first name, last name then in your flow use this format.
- If possible also ask your IT to show some sample records as to how they are stored in the AAD (Azure Active Directory) and which fields are stored.