Hello Gavin and Andreas, apologies for the late response. Could you give more information to reproduce the crash you're experiencing in iOS? I've attempted to reproduce the crash and 202 error and I wasn't able to. For these cases versions are important so if you could provide the Unity Engine version, iOS version, and what iPhone device used to test with.

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.