Hello,
We can help you to fix the issue that you are facing with FTP on your cpanel server. May be some the issue is with any passive ports on the ftp server i guess. AS, you have not provided the error details, I cannot predict the issue.
Please let me know more details and we can fix it asap.
We are professional server administrators having strong knowledge in the field of UNIX/LINUX and Windows.
If you are willing to handover this project to us, you will get future support for all issues from our team.