After upgrading to the latest Playfab SDK, there is a setting to allow for "CompressApiData". This causes a permissions issue on Chrome with a Unity WebGL deployment. I believe most browsers by default enable gzip compression. This redundancy might cause a security error in a browser that breaks the connection attempt with an Unknown Error from the playfab SDK.
We have a temporary fix by adding an exclusion inside PlayFabWWW.cs in the UnitySDK to exclude WebGL on CompressApiData:
+#if !UNITY_WSA && !UNITY_WP8 && !UNITY_WEBGL
This should fix the problem. Let me run a test and confirm.