[Resolved] Several WPML admin pages are not available

Background of the issue:
I am trying to visit several WPML admin pages, but they don't work anymore. The specific pages I attempted to access are: hidden link and hidden link. The issue can be seen on the site: hidden link.

Symptoms:
I encountered error pages: '404 not found' for hidden link and 'No permission to view the page' for hidden link.

Questions:
Why are the WPML admin pages not accessible?
How can I resolve the '404 not found' and 'No permission to view the page' errors?