I have some problems with sidechaing using Sonitusfx compressor in Sonar X2 Essential.
So after I load the Sonitus compressor (vst) in the effect bin of one of my tracks and I want to send another track to its sidechaing input, this input it will not show up in my tracks sends options.  The compressor is working fine on the track on which was loaded but it only does it like a regular compressor. Its sidechaing inputs will not be displayed in other tracks sends option... Same problem with Sonitus gate (I just purchased the whole Sonitus suite). 
Does anybody know how I could make it work? 
My X2 is installed as 64 bit (on Win7), but this souldn't matter because other 32 bit effects are working fine...
Thanks !

Are you sure you didn't just miss it in the list? Sonar has a horrible way of listing send destinations that's messy and confusing when you're looking for a sidechain enabled plug. I know I had difficulty finding the correct one the first time I tried it, and I was convinced it wasn't there. 

I can't see it in the list. I only have my sound card, and some busses (in this case) and definitely no sidechain input for the compressor. I tried to turn off the 64 bit double precision engine but still not showing up in the list . Somehow Sonar doesn't recognise the Sonitus compressor to be a sidechainable compressor...

It may be a limitation of X2 Essential. There is a limit of 5 sends and the Sonitus Compressor and Gate are not part of X2 Essential (at least according to the version comparison pdf)

I believe that may be a misprint, Steve. X1E(and SHS6) had a limit of 5 sends per track.
I can't imagine a 5 send per project limitation being imposed in X2E.
As for side inputs being messy, they are pretty clear in X1E, as seen below.
This may be an issue specific to X2E. I'm on an XP platform, so have not upgraded to X2.
Sorry, Chris. I can verify that it works in earlier versions, but I can't check X2.

Sounds reasonable to me. That send list looks just like it does in X2 Producer. If I had the issue, I would contact tech support.

I sent an email to tech support but no answer yet...
 
What I found out in the meantime is that for a sidechainable VST plug-in to show one sidechain input, the maximum used inputs from "VST plug-in properties" must be set to 4. If set to 2 the plug-in will not show any sidechain input, even if its capable of sidechaining...
(thats: utilities>cakewalk plug-in manager>"select your vst">plug-in properties> set max used inputs)
By default  the "maximum used inputs" for my  Sonitus Fx vst's ( for all compressor, gate etc..) is 2, and it cannot be changed ! If I set it to any other number it will not be saved...
 
This means now that I'm still doing something wrong, there is a bug with my X2a or my SonitusFx compressor and gate are not sidechain capable... So what could be?
 

You may have already tried this, but start a new project template and do it with just two audio tracks (one having the comp)...just to see if it works and somehow the other project itself is messed up. I vaguely remember having a similar issue like this a while back. It was as if the "behind-the-scenes" send routing was borked.
 
I can't see a need to change all those VST settings to make it work. It should work right out of the box.

Problem partially solved... :
I downloaded some free sidechain compressors I found online (Molot on 64bit and    from Reaper ) and  I was able to find their sidechain inputs in the send's list. Also they display 4 max inputs, and they work fine...for free !
 
This means that Sonar X2 Essential has a problem with recognising Sonitus compressor and gate as sidechainable (if they are indeed sidechainable as they say...) in both 32 bit and 64 bit versions.
I'm not sure if this is a bug or some advanced settings related thing (coding?) but I reported it to Cakewalk, just in case...
 
Thanks again for help!
 

Yeah, sounds like a bug. Thanks for submitting the report. Hopefully, it gets noticed.