Hello Andrey and thank you for your inquiry,

For an approach like this I would recommend grabbing the matchState as a Dictionary<string,object> and then making a new instance of JsonMatchState and filling in each field one at a time.

An example of this would look like to get one of the fields:

JsonMatchState matchState = new JsonMatchState();
var matchState = data["matchState"] as Dictionary<string, object>;
matchState.turnNumber = (int) matchState["turnNumber"];

Hope this helps and please let us know if you have further questions or inquiries about this.

Hello Gavin,
Unfortunately I still cannot reproduce the error you're reporting and I've tested against all the devices you've mentioned previously. I would need more information of what your process is in your project that gives you this error that could be helpful for me to reproduce the error. Please provide any and all information or contact us at our intercom on-line chat support to provide an example project or link to project for me to work with. In the meantime I would suggest for you to check out our Authentication Example in our examples-unity repository in Github, perhaps it will provide a solution for you.
Unity Examples: https://github.com/getbraincloud/examples-unity

Hello Gavin,
I'm having trouble reproducing your issue to better give you a solution. What version of Unity Editor are you using? Are you properly initializing on the device before requesting authentication? I have a feeling this might be a permissions issue for network access based on the error message you received. Any other details would be helpful so that I can reproduce this error to find a solution for you.