I know exactly what happened. Their certificate is signed by two (or more, I didn’t actually look closely, but probably two) CA certificates, one of which expired May 30, the other of which isn’t known to your device… with the result that your device (starting May 30) doesn’t trust it and won’t allow a connection. The link I provided in the previous message has more details, and you can also find more information online if you look around. (Presumably RoB isn’t the only service that this affected. The aforementioned article certainly implies as much.)
There isn’t really anything “wrong” with their certificate except what is described in the preceding paragraph. (Multi-signing is harmless except on some broken TLS libraries, which isn’t the case here, and can even be beneficial. In fact, if they had dropped the old CA when switching to the new one, the game would have quit working for the affected players back then.) It’s not even their fault that this happened, really, although it’s certainly unfortunate (if understandable) that this was a surprise, and that there is no official fix yet.
BTW, there are only three resolutions possible:
- Somehow make the new CA certificate available to players that don’t already have it.
- Use a totally different certificate from a CA that doesn’t have this problem (although this may just delay the problem until that CA’s certificates also expire).
- Officially drop support for affected platforms.