Tascam 688 group trouble

[O Burger]

Hello all, straight up noob here. I have consulted these forums many times but this is my first post. I am playing with a Tascam 688 that I may purchase for 50 bux. There is something wrong with groups 1 & 2. Neither will record, but i figured I would just use the others. The problem is that the manual wants me to use 1 & 2 as the stereo mixdown groups. There are outs for all the groups so I figured I would put everything on 3 & 4 for mixdown but for some reason I cant pan between them. Anyone out there who knows their way around a 688 that can give me some advice would make my day. The manual is very basic and it feels like I am missing something obvious. Thank you.

[O Burger]

when mixing with everything grouped to 1 & 2, only 2 works. But i am able to pan between 2 & 1. Also, I am unable to monitor when putting everything on 3 & 4.