Joy
(@joyously)
You would need to give more specifics. Try looking for an error_log file or if there isn’t one, enable DEBUG mode (using logging) to see what you get.
You can use the WP Downgrade plugin to go back to the previous version.
Thank you Joy for your feedback. I could find no reference to the problem in any of the error logs and the DEBUG mode showed no issues. In the end I downgraded as you suggested and the file still does not work! I may have been wrong with my assumption of the cause, so will check everything else I can think of. Many thanks.
Contrary to my previous post, I have been able to confirm for certainty that my JSON script failed after I upgraded to WordPress 5.4. I have since rolled back (using addin WP ROLLBACK) to 5.2.4 and 5.2 and then back to 5.2.4 and in each case the JSON file still failed to work. I suspect it is not a full rollback. If anyone knows a more thorough way to install an older version or has any other ideas then I will be hugely grateful. Many thanks.
Joy
(@joyously)
You are contradicting yourself. (and there is no WP 5.4 yet)
You need to ask someone who knows the code you are using.