Here is what happened:
I updated today, and I launched the game.
It told me to log in to the Activision account. So I tried to log in with my battle net account. But it doesn’t work. And I created a new Activision account. And all my purchased guns and skins are gone！！！what should I do? 
Same thing happened to me, except I may have been hacked as when I open the companion app I see someone else is linked to it now and still has all my stats. I tried reaching out to activisions support, but 3 tickets which I don’t believe were even filed as they never sent me the supposed email confirming the ticket nor were there case numbers attached to the message saying they’ll email me, just “Case#” with nothing following. In my open ticket tab there is also NOTHING THERE. Also tried to use the account recovery in support and go figure it’s broken also “Our system is currently unable to process account recovery requests. Please try again later.” 4 days later still can’t submit a request, just goes to show you multi billion dollar companies really could care less about actually supporting the things they sell us.
Hey man i had the same problem and that same error message. But i believe it is to do with word limit. I had a long essay, i removed the whole thing and put in one letter to test send it and it went through… probably will get rejected cuz of that. Also i used to put MW/COLDWAR/Warzone as affected titles and i changed it to just warzone only. So try that. The support ticket also has a word limit but they dont tell you.