You have activated ServiceMapping plugin but the service mapping home page is blank.
You might still be using UI15 and not UI16
The UI16 plugin is not active.
There is a dependency for Service Mapping home page with UI16.
Activate plugin : "com.glide.ui.ui16"
If this is a non-production instance, with admin role you should be able to activate it yourself from the plugin list.
If this is production, you will have to put in a HI request to have that plugin activated.
Activating this plugin automatically forces all end-users with exception to admin users to use the new UI.
If you need to prevent this you will have to create a property and set it to 'public'. This will not prevent end-users from not getting the new UI, but it will give them the option to switch back to UI15.
See here for more details on the property: