I am working on improving Google Page Speed on a site. As part of this, I made a couple of changes to the js and css loading code in my template.php, installed (and uninstalled) the async_js module, and installed the AdvAgg modules.
Everything works as expected in my local environment. When I checked in and pushed to Pantheon, I noticed that any changes to the performance settings don't get persisted. When I make a change and click "save Configuration", the page displays The configuration options have been saved and reverts back to the original:
Then, before deploying anything to Test, I tried this in the Pantheon Test environment, and the page did persist changes. So I deployed my changes (about 5 or 6 commits). Now it no longer worked in Test, either. I made no other changes, just deployed my commits.
Then I reverted all my commits and pushed to Dev. The page still does not save in Dev, even though, at least in theory, the environment should now be the same as when I started. This always worked locally, and no, there is no reason to believe that caching is causing this. I tried different user accounts in Dev and they all behave the same. There is nothing in the log. I have been pulling my hair out over this for hours and would appreciate any pointers.
Thanks to Clive's suggestion I checked the code in settings.php directly in the Pantheon environment and found this code, and it explains everything .... and yes, the live environment did show the same behavior. Why I thought that the test environment did not, prior to my deployment, I really cannot say.