OnStartGameSession Not Triggering

Hello,

We're using a fresh Third Person Template in Unreal Engine 5, setup everything from this documentation link https://docs.aws.amazon.com/gamelift/latest/developerguide/integration-engines-setup-unreal.html

After uploading the build to Amazon GameLift and creating a fleet from it, we get 2 clients to start matchmaking (our matchmaking rules require 2 players atm), the matchmaking ticket is stuck on PLACING and it's because the game session in the fleet is stuck in Activating state.

Added prints inside the OnStartGameSession lambda and it seems that it's not printing in the server logs.

We're using flexmatch with a queue pointing to an alias that is pointing to the fleet.

What could the issue be?

Thanks in advance.

Elie