I am still encountering issues on client websites with the Update Sites, even after rebuilding it.
Warning Update: Could not open update site #159 "FOF 3.x", URL: http://cdn.akeebabackup.com/updates/fof3.xml Update: Could not open update site #160 "Akeeba FEF", URL: http://cdn.akeeba.com/updates/fef.xml Update: Could not open update site #161 "FOF 4.x", URL: http://cdn.akeeba.com/updates/fof4_file.xml Update: Could not open update site #162 "Admin Tools Professional", URL: https://cdn.akeeba.com/updates/pkgadmintoolspro.xml Update: Could not open update site #163 "Akeeba Backup Professional", URL: https://cdn.akeeba.com/updates/pkgakeebapro.xml Some update sites are disabled. You may want to check the Update Sites Manager. Before updating ensure that the update is compatible with your Joomla! installation.You are strongly advised to make a backup of your installation before you start updating