For a user to appear in the Managers list within a project, they must be a user in both Financials and FinOps, and have the Can be project manager option selected on their resource record:
Also check that the user is in the correct Security Profile in FinOps Administrator to see the Project Management tab.
To add a user to a security profile in FinOps Administrator:
Browse to the hosted gateway link and log in with your cloud details.
Open FinOps Admin and connect to the relevant database.
Click System Control, then click Security Profiles.
Select a profile and click Members.
Find the user ID in question from the list on the right.
Click Add.
Click the three-dot button next to the resource code and select the correct code (the same as the user ID).
Click OK.