Server allow to play only 4 players (HELP, PLS!)

Hi there. I have my own server on And now i have a huge problem, in setting i set maximum players 50, but can enter only 4, other just get kicked with massge “Client timedout”. If i enter when on my server 3 players its fine, but when 4 - i can`t. Other players get kicked too. So the problem in a game engine or server engine or both.
How to fix this problem? (delete addons or set “sv_timedout” 0/3600 not working!).

Server stats: 2x3.0Ghz Intel, RAM 4Gb, SSD 30Gb

Server IP: (developers, try to connect when there is 4 players)