Ah that makes sense. Thanks again for the help.
Both on 4.5. I just realised that the ACF version was slightly different though. 5.3.6.1 was working but for some reason the other installation was stuck on 5.0 which was not. I’ve updated both to 5.3.7 and everything now works! Not sure why that happened or why it wasn’t working on 5.0 but the important thing is it works now. Thanks for pointing me in the right direction.
No JS or PHP errors. But there are also no AJAX requests being made.
On the working version there are three calls to admin-ajax.php with an action of “acf/fields/relationship/query”. The ACF fields are in the main HTML – not loaded via AJAX.
