RP not displaying – “not supported in this context” comment

Seeing a bunch of these and have tried everything listed in the other threads. Having the same issue on a client site hosted with WP Engine. Related Posts is not displaying anything, and is instead emitting this comment: <!-- Jetpack Related Posts is not supported in this context. -->

I’ve followed the Jetpack RP docs and used a filter to keep it from auto-emitting after the_content() and am using the provided shortcode to emit it elsewhere. The Jetpack plugin tells me the site is having issue connecting to the Jetpack service when I debug, yet everything else is working fine and turning off plugins doesn’t fix anything.