What NCM version are you using? I believe I had the same problem and upgrading to 8.0 address it but now puts the html version of notifications into XML tag format.
So found the fix.
So Palo has 4 sections under logging (System, Configuration, User-ID, HIP Match).
On the Palo Alto, instead of sending the configuration messages to Syslog, and setting the alert to look for messages with Commit, I had to create a new System log filter to look for (description contains 'Commit job succeeded') and send those to the Syslog server.
On the SolarWinds server, I changed the Alerts / Filter Rules; I changed the message to *"Commit job succeeded. Completion time*, and it is now working properly.
See screen shot for additional info you run into this problem.