I can’t remember where I first saw this, but occasionally you’ll find that some third party or official import USA and Japanese pads don’t work on a PAL SNES. Very nice of Nintendo to lockout not only games, but pads also! I’ve only seen this on a couple of consoles, but it did confirm that this mod works :-)
Anyway, the fix is easy and you may as well do it at the same time as doing any other mod on your PAL console. Simply link up the 4 points shown. PAL SNES pads will still work on your console after doing this, so there’s nothing to lose.