A 403 error means your server says you don’t have permission to make the request.
This is almost always due to a misconfigured server or an overly aggressive firewall or security plugin.
Security Plugins
Misconfigured security plugins can block Breakdance’s requests, especially:
If you’re using Wordfence, put it into learning mode.
If you’re using another security plugin, consult the documentation on whitelisting requests and avoiding false positives.
How To Whitelist Breakdance Requests
All Breakdance AJAX requests have the URL parameter _breakdance_doing_ajax=yes
Have your host / CDN provider / security plugin / Cloudflare whitelist all requests with this parameter.