Cannot join Zombie Rank Match

Hi Z8 team,
I resubmit the ticket as you demande.
As the title, i can login, play any match, any server, even Normal rank match and Zombie Rank match, but after some game of zombie rank match, i cannot join group Zombie Rank to play (Start) or play alone (Start Directly) any more. The message always say "Failed to join a group (9_0)". It's funny, 1 or 2 week ago i can play Zombie Rank and i reach about 1300 point but now i can't, even if i use "Start directly" to play alone. I send yo you the video (zip file) and 2 screenshot.

PC Hardware: Because the PC wizard is no more, i can't give you the detail report. I have a powerful PC enough to play Crossfire in Ultra setting :
CPU: AMD Ryzen5 2600X
Mainboard: B450 I Aorus
Memory: 32 Gb Ram Ballistix
GPU: GTX 1660 Super 6Gb
OS: Windows 10 Pro 64 bit

In-game Resolution : doesn't matter i think
Server : All channels

Symptoms :
1) Click button Zombie Rank
2) Choose Map or not, doesn't matter
3) If choose Start directly, i received immediately "Failed to join a group (9_0)".
4) If choose Start to join a group, i wait till the group is 4/5 and then i received "Failed to join a group (9_0)".
5) Nothing happen after the message, i must close then play other match type.

Thank you for reading and for the game.
Have a nice day.