Same problem…
New URL (subfolder): https://site.com/new2/
Root folder path of site: /www/site.com/new2/
After click on “Check destination FTP/MySQL connection” folder file /new2/sd_installer.php present, but get error: ‘Could not find file for testing MySQL Connection. Please check “New URL” and “Root folder path of site”‘
If click on “Scan system“, in console get error:
admin.js?ver=0c2ff48…:88 Uncaught TypeError: Cannot read property 'server_stat' of undefinedsuccess @ admin.js?ver=0c2ff48…:88i @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,plupload&ver=0c2ff48……:2fireWith @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,plupload&ver=0c2ff48……:2y @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,plupload&ver=0c2ff48……:4c @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,plupload&ver=0c2ff48……:4