I've tried the tool on ITCM 12.9 and I received the same error. I don't have anything older to test to check where this stopped working. Honestly I wasn't aware of this tool-- is there a particular KB or site where you pulled this tool from?
For CAM/CAF communication issues, most are these are usually due to required ports not being opened:
The above are the basic ports and they need to be opened in both directions.
For CAM, camping is our litmus test. If the camping does not work between two endpoints, then likely UDP 4104 is being blocked or is not reachable.
DNS could also be a factor as well-- is a normal ping of the endpoint name, resolving to the correct IP, in both directions?
If CAM pings are working, but CAF pings are not, there could be a few additional factors--
1- UDP filtering. A default camping sends only 64 bytes of data. When CAF performs a ping or communicates in general, the data is larger, and is possibly being filtered. To adjust for this, you can add "fragment_size = 1024" in your cam.cfg file. 1024 is just a suggestion. This informs CAM to send packets no larger than 1024 bytes. I've seen several cases where UDP is filtered when the packet size is above a particular number, and a cam.cfg is necessary to control the packet size.
2- Certificates. If two endpoints are using custom certificates for ITCM, and those certificates are not matching, then CAF ping would fail.
Hope this helps get you started. I just don't see that tool getting updated in the near future.