Game is out of sync with servers

What you were expecting to happen, and what actually happened?

Play a ranked pvp game

What are the steps to make it happen again?

Play PVP

Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!

This error has occurred for me both on Steam and on Mobile (oddly enough while I was having steam confirm the integrity of its cache. A window pops up and directs me to the support site and forces a restart.

Same here. Restarting the PC-Steam client worked to fix it. On mobile the game doesnt work since two days. Either this out-of-sync message or its stuck on the hero loading bar at 0% on game start right after the login-bar.
Loading the new update, clearing the cache, deleting other games to free up more space, restarting the phone. Nothing did work to fix GoW on my phone.
Is there something hidden in the patch that I cant have the game open on my PC and my mobile at once?
Before I played on my PC and when I went for a smoke or shit I let the client run and took my ohone with me to use the time effectively. Or while traveling from or to work 2 hours each day were my main playtime. Doesnt work anymore.

Just tried it out:
Running the Steam-PC version with chat open and playing on my phone on the same time does work while the chat on my mobile is turned off. Means a change in the chat system brought the problem.