I had this same problem. Try plug the multi tap into the player 2 port (with a controler in the player 1 port) and so on try different arangement for the controllers (mine worked with the way i wrote). If this doesnt help, a friend of mine had a problem with the contacts in the muti tap (or the controlers), if you are experience you could try open it up and make the contacts stick out a lil more or (more preferably) contact the producer of your multitap they may be able to repair it for a decent fee
Can you help me yo, my PS2's controller wont work on Kingdom Hearts 2, Need for Speed Underground 2 and Need for Speed Most Wanted and EA and Square Enix games (excpect for FFVII D.O.G and NFSU and the sims 2)
Usually answered in minutes!