Hi David,

This is a fairly common issue with custom TinyMCE plugins in CMS 12, and it usually comes down to how and when the plugin is registered and loaded, rather than the plugin code itself.

A few key points to be aware of in CMS 12:

1. CMS 12 loads TinyMCE via AMD / Dojo (not global TinyMCE)

Unlike older CMS versions, CMS 12 does not expose TinyMCE globally.
If your plugin assumes tinymce is available on window, it may work locally but fail in CMS.

Your plugin must be registered through the TinyMCE configuration, not via a standalone JS include.

2. Correct way to register a custom TinyMCE plugin

You should register the plugin using TinyMceConfiguration (or TinyMceConfigurationBuilder), for example:

[ServiceConfiguration(typeof(TinyMceConfiguration))]
public class CustomTinyMceConfig : TinyMceConfiguration
{
    public CustomTinyMceConfig()
    {
        AddPlugin("myplugin", "/ClientResources/tinymce/myplugin.js");
        Default()
            .AddPlugin("myplugin")
            .Toolbar("bold italic | myplugin");
    }
}

Important checks:

• The plugin name must match the name used in tinymce.PluginManager.add

• The path must be accessible (check Network tab for 404s)

• The plugin must be added to the toolbar, otherwise it won’t appear

3. Plugin JS must follow TinyMCE plugin pattern

Your plugin JS should look like this:

tinymce.PluginManager.add('myplugin', function (editor) {
    editor.ui.registry.addButton('myplugin', {
        text: 'My Plugin',
        onAction: function () {
            editor.insertContent('Hello world');
        }
    });
});

Common mistakes:

• Plugin name mismatch

• Using deprecated TinyMCE APIs

• Trying to access CMS-specific globals inside the plugin

4. Clear browser + CMS UI cache

TinyMCE plugins are aggressively cached.

After changes:

• Hard refresh browser (Ctrl+Shift+R)

• Reset CMS UI view:
  Profile  => My settings => Reset views

• Restart site if plugin registration changed

5. If plugin works locally but not on DXP

Check:

• File included in deployment package (ClientResources)

• Correct casing in file paths (DXP is case-sensitive)

• No bundling/minification stripping the plugin file

6. Debugging tips

• Open DevTools => Network => look for your plugin JS file

• Check Console for:

  • Plugin not found

  • Cannot read property 'PluginManager'

• Temporarily log inside plugin JS to confirm it loads

Hope this will helps you !