Steam authentication error (OperationResponse 230: ReturnCode: 32755)

Hi! We're trying to authenticate users via Steam. This worked a few weeks ago, but now when trying to connect we're getting CustomAuthenticationFailed, and this error:
OperationResponse 230: ReturnCode: 32755 (Unexpected character encountered while parsing value: <. Path '', line 0, position 0.). Parameters: {} Server: NameServer Address: ns.exitgames.com:5058
UnityEngine.Debug:LogError(Object)
Photon.Realtime.LoadBalancingClient:DebugReturn(DebugLevel, String) (at Assets/Photon/PhotonRealtime/Code/LoadBalancingClient.cs:2480)
Photon.Realtime.LoadBalancingClient:OnOperationResponse(OperationResponse) (at Assets/Photon/PhotonRealtime/Code/LoadBalancingClient.cs:2560)
ExitGames.Client.Photon.PeerBase:DeserializeMessageAndCallback(StreamBuffer)
ExitGames.Client.Photon.EnetPeer:DispatchIncomingCommands()
ExitGames.Client.Photon.PhotonPeer:DispatchIncomingCommands()
Photon.Pun.PhotonHandler:Dispatch() (at Assets/Photon/PhotonUnityNetworking/Code/PhotonHandler.cs:223)
Photon.Pun.PhotonHandler:FixedUpdate() (at Assets/Photon/PhotonUnityNetworking/Code/PhotonHandler.cs:149)

The client side code is more or less identical to the example, from what I can see.
var values = new AuthenticationValues(token.Userid);

values.AuthType = CustomAuthenticationType.Steam;
values.UserId = SteamUser.GetSteamID().ToString();
values.AddAuthParameter("ticket", Token);

PhotonNetwork.AuthValues = values;

PhotonNetwork.ConnectUsingSettings();

The steam app id and web key on the Photon dashboard should also be correct. Calling the Steam web api directly using our settings and a generated ticket works as expected.
It's not a very helpful error message. It looks like the server is receiving HTML, when it's expecting JSON? But it seems to correctly handle other errors that can make the web api return HTML (e.g. misnaming the "ticket" parameter).

Any clues to what's going on here and what we can do about it?

Comments