X1a - MIDI not recording

Did you arm the track prior to hitting record?

I take it when you say synth is audible you are using a mouse versus the keyboard to trigger it. Yes?/No?

If yes then it sounds like you do not have the midi controller pointing to the synth in Sonar. It's working but just not aligned to the synth module. Check the output of the midi track and make sure your synth is selected. Then check the controller, bank and patch to make sure they are selected for the sound you want.

How do you know the synth is audible, can you let me know that?
Also, did you hit the record button once the midi track is armed. I know, dumb question but some people think they can just hit play.
 
Last but not least, try this:

Your controller usually has a setting on it called Local On/Off. When your controller is connected to your interface, you need to set the Local On/Off setting to Local Off. That’s because if your software is set to send MIDI messages back to your controller, when you play a note on your controller, it is sent to the computer, and then back to the controller again through its MIDI IN, causing it to play two notes every time you play one note on it. When your controller is set to Local Off, it won’t play a note on the controller when you press a key, but only when the Note On message comes back from the computer, which happens instantaneously. Remember to set it back to Local On if you’re going to use the controller separate from the computer.

Let me know how that is set.

What channel is the XP30 transmitting on? Is this the same as the channel setting in the midi track?
 
Also, just for my sanity, is the EDEROL selected as a midi device or perhaps is sonar viewing the keyboard? Is the keyboard set up as a controller in X1 with the Ederol ins and outs chosen?

Glad you got it sorted out.