When I try to log in to my cPanel I get an error message saying: "Not found. The server was not able to find the document (./frontend/x/index.html) you requested.". Why?
You bookmarked an older theme of cPanel - the so called x-theme. With the new cPanel there is also a new theme name called x3. Please use one of the ways as described in our knowledge base article #189 to connect.