App Engine Flex Compatibility

Hello support… I am hoping you can assist me. I am running your plugin on App Engine Flex and am trying to enable the “App Engine Compatibility Option.” I will note that I am unable to “enable” App Engine compatibility.

I am running wp-stateless in stateless mode and I am running a network install (multisite) of WordPress. Nothing that I do will allow me to “enable” the App Engine compatibility option. Is there some sort of setting that I am overlooking which is preventing me from being able to enable the compatibility mode? Is there a define command that needs to be added to wp-config?

Any help would be appreciated. The option remains grayed out in the Network Admin Settings and the Local Site Settings. I cannot enable it. Which is odd. Because as I said, I am running this on App Engine Flex.