The “not a valid JSON response” error in WordPress usually means the editor cannot complete a REST API request. The fix is to isolate whether the failure is caused by permalink, rewrite, SSL, plugin conflicts, or server rules.
1) Verify site URL and SSL consistency
- Both
WordPress AddressandSite Addressshould use the same host and HTTPS state. - If you use Cloudflare, ensure origin and edge SSL settings are aligned.
2) Reset permalinks
Go to Settings -> Permalinks and click Save. This rebuilds rewrite rules.
3) Check REST endpoint directly
curl -I https://www.wordpresshosting.solutions/wp-json/
curl https://www.wordpresshosting.solutions/wp-json/If this fails, the editor will fail too.
4) Test for plugin/theme conflict
wp plugin deactivate --all
wp theme activate twentytwentyfourThen re-test editor updates. Re-enable components one-by-one to find the trigger.
5) Review server and firewall rules
- Confirm no rule blocks
/wp-json/. - Check WAF/Firebase/Fail2Ban patterns that might block admin requests.
- Inspect Apache/Nginx logs for 403/500 on REST calls.
6) Validate file permissions
Incorrect ownership can break media and post updates.
sudo chown -R www-data:www-data /var/www/wordpresshosting_sol
sudo find /var/www/wordpresshosting_sol -type d -exec chmod 755 {} ;
sudo find /var/www/wordpresshosting_sol -type f -exec chmod 644 {} ;Most sites recover after fixing rewrite + REST access + mixed SSL settings.
Validation
Re-test key user paths and review service logs after each change.
Further reading: WordPress Troubleshooting Guide
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