On a project that I'm working on, our scope of work has been complete since July of 2021 and the building has been occupied for roughly a year. We still haven't seen retention payment for this project. When do owners/GC's need to pay retention?
Payments must be made according to the terms of the contract. Unless there are incomplete punchlist items, there should be no justification for the customer to continue holding retainage.
You will need to bring a law suit likely to get them to pay retention. They may argue they do not have to pay retention until the all punch list items are done. But if the place is occupied you should be able to get paid unless you have outstanding work that needs to be done.