Ace Editor not working
Checklist
Clear IE cache: Close SAP GUI and all IE Windows. Close SAP-Logon. Start Microsoft Internet Explorer and clear the browser history.
Preview URL: If your SAP system has a different URL that should be used for Web Access, setup Settings→System the preview URL to the right URL.
Update your host file: In Windows Explorer go to \Windows\System32\drivers\etc and open file 'hosts'. This file contains the mappings of IP addresses to host-names. Add entry of your SAP system: <ip address> <hostname>. Save 'hosts' file.
If it still does not work → please tick "Use old Editor"