[Macluawn]

You have parameters messed up. You are trying to search for your name in tag [GC] and thats why it isnt working
https://sampwiki.blast.hk/wiki/Strfind

EDIT:

pawn Код:

new pname2[24];
GetPlayerName(playerid, pname2, sizeof(pname2));
if(strfind(pname2, "[GC]", false) != 1); 
{
    SendClientMessage(playerid, RED, "Found");
}
else
{
    SendClientMessage(playerid, RED, "Not Found");
}