No. The odd thing is that the CM15A is in a different panel than the LM14A's that work. The LM14A's that don't work are in a different panel. I assume that the signal is sent over the wire and not RF. Correct?? What devices would be phase coupling or repeating devices?
The "phases" of your electrical system are repeated in each of your panels (assuming you have 220V split phase which is common). Each panel will have a phase A and B. Devices located on phase A will have a much easier time communicating with other devices on phase A. Without a coupler, devices trying to communicate across phases (A to B) will need to travel outside your home and through the power co. transformer (significant signal loss).
If you have a single power drop from the electric co. (be sure to check that you do have a single meter), an active coupler should help.
Like you, I have 300A service split among multiple panels (lot's of toys - welders, air compressors, etc). I use a Leviton HCA02 active repeater in my main panel. It has served my well, but is now becomming a bit undersized. I'm guessing that your home is quite a bit larger than mine. You'd be well advised to look at the recommendations that Dave_w provided (I've been looking at the XTB-IIR myself).