@Hoobiechoobie Hi, I believe I'm having the same problem. On the 25/08 was the first time I seen the Playfab error. It appears as I enter the main menu, then again if I try and enable crossplay.
I tried the connection guide when it happened, Then your recommendations tonight but it's the same. The only workaround for me was to game share to a new steam account. I log out of the account the game is purchased on, log into the second account and crossplay works fine. Even my saved replays from the original account are still there.
The other thing I noticed but I'm not 100% here and going off memory. With one of the recent updates (last two weeks) I'm almost positive I had to re-agree to the T&C's pages at game launch. This was on the second account after already using it for a few weeks .... Tonight when trying my original account with the Playfab error, It's been unused for since the 25/08, I didn't get any T&C's request at game launch. Could it be something as simple as for whatever reason were aren't able to accept the T&C's and therefor cant enable crossplay.
I'd also be happy to try the extended logging or even sharing my steam account if you guys are struggling to replicate the error. I've tested my account on 3 separate PC's at 2 different locations so I'm sure it would be the same for anyone using my account. I'll DM to sort this.
In answer to the above questions
Steam.
Game sharing to a different steam account works.
Yes I raced in both crossplay preview periods.
Thanks