Is ppt Puyo Puyo Tetris? Best to note that sort of thing in these discussions as not everybody might as versed in the games/franchise you are looking at but might otherwise have been able to help you. Especially as the DS does not feature Puyo Puyo Tetris as far as I know and that means you are trying for a cross platform port which can be its own problem (not that intra platform does not have its own issues), though if it is wave file to wave file then the usual guess is you did not match the format used by game you are going to (stereo/mono, sample rate, bit depth...) or care to make the game use (many DS games dropped audio quality to save space, you can alter what the game expects to get higher quality going on).
I also presume you are using the DS version of puyo puyo fever 1 for this rather than gamecube or GBA or whatever?
Does the game use the SDAT format or something else? What tools are you using for this (generally speaking I am not a fan of most SDAT rebuilding tools or import tools, )? Is this one of the games that lost voices when it left Japan as other than format differences that is one of the big ones?
Working but disabling opponents can mean many things from you failed to rebuild the sound files properly, to the format stuff, to the format stuff but if it was higher quality then it might be using more resources and the game consequently fails to load the other.