This is thankfully solved. Yes, the key boxes were TRACK MUTE/SOLO and TRACK AUTOMATION. Really grateful for your help.
And I do NOT know why the box checking didn't do anything when BRISTOL JONESY suggested that above.
You guys are the best. AND, btw, once I got this working right, I also tested everything with the MASTER BUSS and it works as well. Now I'm a friggin' professional, right? :)
Thanks to all.