BUG in PUN: Specified cast is not valid

We have a project that uses PUN to play multiplayer in Unity. At first we tried the free version and were able to work. But once we move on to the full plugin, we get stuck in the login stages. Attach the errors in the console.
We will be happy for a solution.
Thanks

THE ERRORS:
InvalidCastException: Specified cast is not valid.
Photon.Pun.UtilityScripts.CountdownTimer.TryGetStartTime (System.Int32& startTimestamp) (at Assets/Photon/PhotonUnityNetworking/UtilityScripts/Room/CountdownTimer.cs:153)
Photon.Pun.UtilityScripts.CountdownTimer.Initialize () (at Assets/Photon/PhotonUnityNetworking/UtilityScripts/Room/CountdownTimer.cs:123)
Photon.Pun.UtilityScripts.CountdownTimer.OnRoomPropertiesUpdate (ExitGames.Client.Photon.Hashtable propertiesThatChanged) (at Assets/Photon/PhotonUnityNetworking/UtilityScripts/Room/CountdownTimer.cs:116)
Photon.Realtime.InRoomCallbacksContainer.OnRoomPropertiesUpdate (ExitGames.Client.Photon.Hashtable propertiesThatChanged) (at Assets/Photon/PhotonRealtime/Code/LoadBalancingClient.cs:4027)
Photon.Realtime.LoadBalancingClient.ReadoutProperties (ExitGames.Client.Photon.Hashtable gameProperties, ExitGames.Client.Photon.Hashtable actorProperties, System.Int32 targetActorNr) (at Assets/Photon/PhotonRealtime/Code/LoadBalancingClient.cs:2070)
Photon.Realtime.LoadBalancingClient.OnEvent (ExitGames.Client.Photon.EventData photonEvent) (at Assets/Photon/PhotonRealtime/Code/LoadBalancingClient.cs:3077)
ExitGames.Client.Photon.PeerBase.DeserializeMessageAndCallback (ExitGames.Client.Photon.StreamBuffer stream) (at <a497a6f18e1f4b419421b940add27a6e>:0)
ExitGames.Client.Photon.TPeer.DispatchIncomingCommands () (at <a497a6f18e1f4b419421b940add27a6e>:0)
ExitGames.Client.Photon.PhotonPeer.DispatchIncomingCommands () (at <a497a6f18e1f4b419421b940add27a6e>:0)
Photon.Pun.PhotonHandler.Dispatch () (at Assets/Photon/PhotonUnityNetworking/Code/PhotonHandler.cs:208)
Photon.Pun.PhotonHandler.FixedUpdate () (at Assets/Photon/PhotonUnityNetworking/Code/PhotonHandler.cs:142)