External Insert Plugin Setup?

Could you be specific and, looking at the whole signal chain, tell us which meters are moving and which ones are not.

Kev999
Could you be specific and, looking at the whole signal chain, tell us which meters are moving and which ones are not.

I can see the signal coming in on the plugin but the only sound going out when I turn up the input knob on the MX200, is feedback.

I think you need a double set of outputs on your sound card to do this.  1/2 and 3/4.  Use the 3/4 to rout out to external hardware, which will then rout back to 1/2, eliminating your feedback loop.

Disable the input monitor icon in the track and use the record icon to give you meters?
 
Added: https://support.focusrite...an-insert-when-mixing-

I have an MX 200 and a Focusrite 6i6. The MX 200 can actually be set up as an external device via the USB connection too. It would show and behave as a VST.   This was working in Windows Xp and possibly W7 32 bit how well I have no idea not much info out there about it. I tried installing the software to W 8.1 and it wouldn't go. I didn't try very hard and there might be someone who got it working on W 10 in compatibility mode.. Someday I might take the time to figure this out as the effects in the MX200 are certainly a cut above ones I have as VST's. At this point I only use it in my live rig. But hooking it up in Sonar is not that hard to do. 
 
 
First you'll need to start with setting a custom mix to 3/4 output. The default is a clone of 1/2. You'll need to get the hang of Mix Control and the stupid wording they use like DAW 1 etc. 
Connect output 3/4 to the input of the MX200
Send the output to in my case inputs 3/4 of the interface ( use line inputs) 
You can set the MX 200 to 100% wet. 
Create a new Buss name it MX200 and set the outputs to 3/4. 
Now send some tracks to that as an effects send. 
Insert a stereo audio track and select 3/4 as input. 
Now when you record this track it will record the wet output of the MX 200. 
 
This is not a great way to work as if you make any changes to the tracks you applied the MX200 too they will have to be re done via the MX200 recorded track.  Just not worth the bother but it can be done.. This is why it would be nice to get the USB system working as that's the only practical way to use it effectively ( pun intended) 
 

Cactus Music
I have an MX 200 and a Focusrite 6i6. The MX 200 can actually be set up as an external device via the USB connection too. It would show and behave as a VST.   This was working in Windows Xp and possibly W7 32 bit how well I have no idea not much info out there about it. I tried installing the software to W 8.1 and it wouldn't go. I didn't try very hard and there might be someone who got it working on W 10 in compatibility mode.. Someday I might take the time to figure this out as the effects in the MX200 are certainly a cut above ones I have as VST's. At this point I only use it in my live rig. But hooking it up in Sonar is not that hard to do. 
 
 
First you'll need to start with setting a custom mix to 3/4 output. The default is a clone of 1/2. You'll need to get the hang of Mix Control and the stupid wording they use like DAW 1 etc. 
Connect output 3/4 to the input of the MX200
Send the output to in my case inputs 3/4 of the interface ( use line inputs) 
You can set the MX 200 to 100% wet. 
Create a new Buss name it MX200 and set the outputs to 3/4. 
Now send some tracks to that as an effects send. 
Insert a stereo audio track and select 3/4 as input. 
Now when you record this track it will record the wet output of the MX 200. 
 
This is not a great way to work as if you make any changes to the tracks you applied the MX200 too they will have to be re done via the MX200 recorded track.  Just not worth the bother but it can be done.. This is why it would be nice to get the USB system working as that's the only practical way to use it effectively ( pun intended) 

 
Thanks, Cactus! All setup and ready to go! :) (high five)