You're doing this for mixdown, not for tracking, right? that's what it sounds like, anyway. My post above assumed that you were tracking.
Okay, I'll assume that you have ADAT track 11 coming in through tape monitor in 11. You have three pairs of aux busses available: aux3-4 as a pair, aux5-6 as a pair, and mon1-2 as a pair. So let's set up aux 3 for this, just as an exercise. Set up the board's channel 11 to take its input from tape monitor 11, not from mic/line in. Bring up aux3 on channel 11, routing your dry signal off onto aux3 of the aux3-4 pair. Patch the aux 3 output to the M-one's input. That's your dry send to the effect. Aux 3 is post-fader, so your fader moves will control not only the dry level, but also the level sent to the M-one.
Patch the M-one's output back to channel 12's line in.
Set up channel 12 to listen to mic/line, *not tape*. That's your wet effect.
Now, you have wet and dry available. What do you want to do with it? If you're mixing down to stereo, then you can route both channel 11 and channel 12 to the left/right main mix, pan and eq them as you like, and control the relative levels of dry and wet with the channel 11/12 faders. Fader 11 affects only the dry level and send to the effect, fader 12 affects only the wet level (return from the effect).
If, instead, you want to print this back to another track, you can do it one of two ways: route the wet (effected only) version back to its own ADAT track, so that you can mix wet and dry later. Or you can mix wet and dry right now and print *that* back to its own ADAT track, which would require you to use a submix.
To do the latter, you'd route both 11 and 12 to a sub (say group1-2), and pan them hard left to put all the signal on group 1. The balance between wet and dry will be controlled by the channel 11-12 faders, and the overall level will be controlled by the Group 1 fader. Patch the output of Group 1 to an ADAT track record input, and you're ready to print the wet+dry mix back to the ADAT. At that point, you could even choose to reuse track 11 for something else, if you like, since your new track will have the vox+effects you wanted.
That may be too much work for what you're trying to do. If you use the channel insert, you don't have to use up another channel: important if you already have 16 tape tracks recorded that you need to mix. Similarly, if you patch the ADAT's out 11 directly to the M-one's input, you can then patch the M-one's output right into the track 11 line in, and use the knob on the M-one's front panel to control wet/dry. You can accomplish the exact same thing by using the channel 11 insert: that just lets you do it without unpatching the ADAT from the tape monitor in at the board...
There's more than one way to do it. In fact, there are probably 20 ways to do it! And which one you choose depends on what you're doing: tracking, bouncing, mixdown.. and how easy it is to reroute signals within your rig.
I'd still bet that your initial problem was mislabeled send/return plugs on your insert cable. Try that first of all, so that you aren't trying to revamp your working style and get work done all at once! Swap 'em, and I'll bet a beer that things start working.
One word of warning, and an apology. I also just checked
my Studio 32 manual, and discovered that I had it absolutely wrong: the 32's inserts send on the tip and return on the ring, Mackie-style, and *not* the way I described it above (A&H/Soundcraft style). Serves me right for working from memory, instead of looking it up. Aw, hell, I slept since I wired my patchbay- and I haven't had to deal with that since then: I just know my old insert y-cables are labeled backwards for the Panasonic.... Mea *maxima* culpa. Sorry if that added to your confusion.
Which means I'm going to have to redo the inserts in my patchbay when I get my Ghost. Wah.