if you enter a hide and seek server they usually make it so you have to have radar off, so it isn't really easy to spot where they are if you're looking at them
to turn it back on try typing cl_radaralpha 200
the cl_radaralpha 200 didn't work?? - thats the only thing that can take away the radar, unless you have sv_cheats 1, in order to have cl_hud 0 - which would cause you to get banned from basically every server you connected to