Hello @domesticempire,
this can show up when the SecRuleEngine option from the Apache mod_security module is set to “On” instead of the “DetectionOnly” and the Custom Code you’ve tried to add included JavaScript code or HTML tags that trigger the mod_security rules.
You could try contacting your hosting company and ask them about the SecRuleEngine option from the Apache mod_security module. If it is enabled, then any method (a plugin, or the “WP Admin -> Appearance -> Theme File Editor” page, or through one of theme’s options) you might use for adding the JS or HTML custom code through the browser will lead to the “403 forbidden” error.
If that is the case, then you could switch the option to “DetectionOnly”, or you could choose to add your JS/HTML custom code to the child theme’s files and upload them to the server through SFTP or SSH.
Thank you Diana. I shall explore those options and see what works best 👍