error when trying to create a game

I have recently deployed Photon Server and ran Load Balancing as a service, everything works fine until there are about 1k CCU, when I try to create a game i get this error on the client side :

Operation failed: OperationResponse 227: ReturnCode: 32762 (Failed to get server instance.). Parameters: {} Server: MasterServer

there are no overload on the cpu, and its is running at 21%.

what causes this issue?

thanks.