Cross-posting from PSCLOUD-43638:
Let me address the multiple clientKey issue which has come up in this discussion. Whenever a Jira instance performs an import, the clientKey for that instance will change. In addition, Connect addons are not imported. So it would not be unusual for a site to be imported and then Connect addons reinstalled following the Import.
In that scenario you will receive multiple install payloads for the site over time, with different clientKeys.
I believe this site has undergone two imports which would explain why you have received three clientKey values.
Please can someone at Atlassian get the docs fixed? This is important information for vendors to know about.