Client lag in Matchmaker

Hi , I have a little problem with my network game.
There is a significant delay when the client presses the input button and its movement, and it only happens with the client and only in matchmaker , even when trying to join a game it takes a long time in the client. First I thought it's because I have many Command functions , but I found that this is not the problem.
please help me , it's been more than a week since I had this problem !