When installing on WP Engine, you will need to contact WP Engine support and request that they turn off the “redirect_bots” setting, and purge the cache.
If this setting is not disabled, then it will not be possible to send HTTP POSTs to your app, as the WP Engine server will intercept and stop them from succeeding.
You’ll need to send a support ticket to WP Engine Support and ask them to allow your posts to contain variables.
Here is a sample ticket you can send to them…
We’re using Infusionsoft and we need to send an HTTP Post to our WordPress membership site to set a password. The HTTP Posts that are being sent to WPEngine return an Unexpected 301 result if you have a query string added to your post URL.
For instance this will fail: http://site.com/?operation=makepass
But this will work: http://site.com/
Can you please modify our nginx configuration for this install to allow variables on our HTTP Posts? And can you turn the “redirect_bots” setting off on my hosting account?
Since Infusionsoft now uses a wide range of IP’s (because they are now using Google Cloud Services) when running HTTP POST’s, can you also please whitelist “Infusionsoft” (without quotes) in HTTP POST header “User-agent” field?
If you’ve already made this change and are still seeing the warning notice, you can disable it by clicking “Hide this Notice” in the bottom right corner of the box.