supercustom limited right speakers not working

hi everyone,
just brought a 1997 super custom limited and loving it, over the weekend i replaced the headunit and used the toyota to iso harness (Aerpro APP0141) everything worked as it should apart from the front and rear right speakers. there were a bunch of other plugs used for a navigator system and others that i'm not sure about. has anyone else came across this issue?
ive been reading about them having a hidden amp which i'm assuming is probably affecting it?

Were they working before?
Was it an original Toyota headunit?

On mine I found a Yaris adapter did the job, if you can see if you send a signal down the speaker wires that are not working. I.e. disconnect the heat unit and use an AA battery to send pulses down to the speakers. Do the left and then the right (they are colour coded on the Iso adapter) and see if you get anywhere.