I just tested this new release with Rapture Session, and both the Chords and Arp functions worked just fine.
 
Even though Step 4 is all CAPS, do you have BOTH MIDI tracks armed for Input Echo?
 
Of course, I was following my own instructions, so maybe there's something that, to others, is not clear in them. If there's something you find, please let me know, so I can update them. Thanks in advance.

v1.15 is working fine for me with Sonar (and Studio One3 and Cubase 8.5).  I just tried the arp section alone and it worked fine, and it worked with the chords on and off.  Chord worked with arp and without it.
 
Don't know why it is not working for you.  Sorry.

 I'm not sure what's going on either.....I even set up a new project with Cthulhu and Alchemy just to test out this problem and made sure I followed those instructions to a T (including "BOTH MIDI tracks armed with Input Echo").........no luck.
 
To be honest, I'm not sure how to even trouble shoot this; other than just clicking on different input/outputs to see what might actually work. The only sound I can get out of Cthulhu is the internal synth (purple speaker) and of course Alchemy (when playing my midi controller keyboard). 
 
If you guys aren't having these issues, then it obviously HAS to be something I'm doing wrong.........   
    

Sorry, Mesh. Here's a pic of my working routing. Maybe something in it will help.
 

I definitely think there is something wrong with this update. It's not saving its state properly with the project. I had an awesome arp thing going last night as the result of an hour of meticulous twiddling and I saved the project. Loaded it up this morning and it's completely gone - Cthulu is just playing what sounds like the "Chords2Chords" preset or something. This is the second time it's lost its state in a project for me. 

TheMaartian
Sorry, Mesh. Here's a pic of my working routing. Maybe something in it will help.
 

Thanks John, I appreciate the pic......I'll definitely use this tonight and see what's going on.
 
 
Sharke, that's got to be frustrating as well....spending that much time on something and then lose it.
 
Is there a way to revert to a previous version of Cthulhu (besides going through Windows 10 earlier date)? 

I checked it out (briefly last night) and my setup is identical to yours John (except the output on Cithulhu (on mine) goes to Master (IIRC). Found out some strange things were going on with this plugin.....
 
On the same project (Cthulhu, Alchemy, and also BlueArp (just to play around/test)) was opened.
I just pushed 1 key on my midi controller and could hear BlueArp + some odd scale (diminished to outright weird notes) were playing.
 
I deleted the BlueArp and only had Cthulhu + Alchemy.......now, the Arp function and Chord function both worked. Of course, it started playing some very high pitched arp patterns when I pressed low notes on the controller and some weird patterns (nothing melodic) were playing. Adjusted/tested/pushed buttons and other patterns in Arp & Chord and then they both played as it should.....
 
I really don't know what caused it nor what triggered it to work...... most peculiar mama.
When I have more time, I'll try to figure out what caused it.....
 
 

So it sounds like you have functional use of Cthulhu. Great!

Yeah, I have a functional dysfunction in my junction.  

Way to go, Meshman!