I'm having the same problem as the OP. I've tried the steps you provided, ridhijain.
Here's how that went:
1. Attempted "Issue Confirmation" and cannot locate the statement “Package signature validation failed” in the log. This is what it says though after attempting to install my app: com.apple.xpc.launchd[1] (com.apple.xpc.launchd.oneshot.0x10000008.Adobe AIR Application Installer[2157]): Service exited with abnormal code: 7
2. I went ahead and tried the "Solution" steps just in case, but couldn't get past extracting the .zip file after renaming. It just creates a new zipped folder every time I unzip it. So, stuck on that step.
You can see the app that I'm trying to install via this link and the file is named see.air: Sibelius - the leading music composition and notation softwarehttp://www.sibelius.com/download/sse/main.html
I've actually already contacted the author (Avid) first, as the error message suggested, and they seem to think it's an issue with Adobe and have directed me to this forum.
Here are my system specs in the event it makes any difference:
MacBook Pro 9,1 (15-inch, Mid 2012)
Processor: 2.6 GHz Intel Core i7
Memory: 16 GB 1600 MHz DDR3
OS Sierra 10.12.6
Latest version of Adobe Air: 27.0.0.128
Please offer a solution and/or confirm whether the issue lies with Avid and not Adobe. They are basically putting it up to me to find a solution unless you all are saying there is no issue.
Thank you!