I've found the ARM button on the VS-700C can be a bit flaky at times.  For instance, it flatly doesn't work on the first channel strip on some of my projects.  It works fine on other tracks (except for instrument tracks--see below), and if I move the track to another strip on the console, it also works fine. 
 
The other problem I've noticed is with instrument tracks.  I can arm them with the button, but the red light on that strip doesn't come on (although the master ARM light to the left of the channel strips DOES come on) and I can't un-arm the track by pressing the button again.  Flaky.  It does not do this on MIDI or Audio strips.
 
Anybody else have this trouble?  I haven't checked all my projects or tried to narrow the problem down any more than this, yet.  Working on it!  But there's definitely something buggy happening.  I'm hoping it's not my button (the light DOES work, if I ARM a track and then move it to the first strip)!  Feel free to chime in...

Additional Info:  I just opened up the VS-700C Console using MIDI-OX and the button IS working (whew).  So...the problem is definitely within Sonar somehow.

I to am having track arm problems with my VS-700C. I am able to arm but not disarm any v-synth tracks. Audio tracks appear to work fine. This problem started right after the X1d update. I contacted support and hope they can provide a fix for it. I am sure it is just a broken definition.

I to am having track arm problems with my VS-700C. I am able to arm but not disarm any v-synth tracks. Audio tracks appear to work fine. This problem started right after the X1d update. I contacted support and hope they can provide a fix for it. I am sure it is just a broken definition.

 
I'm actually moving away from Instrument Tracks altogether, partly due to the above problem, but mostly due to the inability to easily view/edit MIDI data, including (and especially) CC envelopes.  Maybe after all the MIDI is done and it's time for mixing, it might be useful to recombine the tracks.  We'll see how it goes. 

Don't have the problem here but I suspect the issue you are seeing directly relates to midi. There is a little oddness now with the 700C using X1 and I'm happy to stay away from the direct midi side of things here... seen a few weird midi issues and usually when a 'customer' is watching or waiting to track. Tonight I lost surface control of eq after using ACT for a different reason.... disappointing it's become a little unpredictable when it starts to interrupt your workflow. Hope you get your issue resolved. Cheers.

Instrument tracks have always been flawed. It's sad to see the console (and VS-700c) being cluttered with so many double tracks (Audio & correspondend MIDI).

Instrument tracks have always been flawed. It's sad to see the console (and VS-700c) being cluttered with so many double tracks (Audio & correspondend MIDI).

 
You're right, and it seems like there must be a more elegant solution.  Something to look forward to in future versions, I suppose.

For instance, it flatly doesn't work on the first channel strip on some of my projects.

 
I solved this mystery!!  I use the transports on several of my MIDI devices...like my trusty old VM-3100 Pro, controller keyboard and some MIDI pedals.  To do this, I set the MIDI "Shift key" parameter to the lowest note, C0.  Turns out the VS-700C uses that particular MIDI note to control the ARM function on the first channel strip.  Other notes play nice, but due to the way the "shift key" works it gets nixed.

I'm not sure what the work-around will be, other than selecting another note for the shift key (and running the risk of killing another function on the console).  Maybe the very tippy-top high C.  I could use a CC message instead, but I think the VM-3100 can only send notes.  Maybe it's time to give up on the VM-3100 transport, anyway, since I don't really NEED that old thing, with this big beautiful VS-700C sitting in front of me.  But I do need the other transports for remote control while tracking.
 
ANYWAY...
 
So that just leaves the one issue with ARMing Instrument Tracks, which appears to be a known bug.  For that, I guess we just wait and see...

A more elegant solution. Use ACT learn on your controllers and it should find a suitable channel.

more elegant solution. Use ACT learn on your controllers and it should find a suitable channel.

 
That would work fine with my VM-3100 PRo, but isn't practical with controller keyboards or pedals, since I don't want ALL the MIDI intercepted.  I did set up the VM-3100 as an ACT controller and it worked fine, but decided I didn't really need the extra controls with the VS-700.  It's good to have the option available, though.