No, it has nothing at all to do with the "IPv6 issue". Note that your FTP client fell back to IPv4, made the connection, and allowed you to upload your files. You checked with the cPanel file manager, which shows you that the files are on the server, and inside the public_html directory, where they belong.
(Your FTP client is designed to try IPv6 first, but IPv4 still runs most of the internet. There are many, many times more IP addresses available in the IPv6 scheme, so when everybody has their car, fridge and toaster hooked up to the "internet of things", there'll still be enough addresses to go around.)
bdistler gave you a link to a set of troubleshooting instructions for the blank page problem. Try following those. And try to get some sleep; your web site isn't a life-or-death issue.