I think there's a case of apples:oranges:bananas going on here.
Your website at gosportwx.com appears to be hosted at GoDaddy.
http://gosportwx.com/ and
http://www.gosportwx.com/ both end up at the same location (your website) as GoDaddy treats both URLs as the same. The browser is only looking up your domain name for the connection anyway, and both the gosportwx.com and
www.gosportwx.com DNS lookups return the same IP address.
Currently, neither the www. and the plain domain have a valid certificate, so https:// to either does not work. Getting an SSL certificate from GoDaddy can be an expensive proposition or you can use the fairly complicated
https://www.sslforfree.com/ to generate LetsEncrypt certs and the directions on how to do that with GoDaddy .. that would allow you to offer https:// to your site.
GRLevel3 currently only used FTP (not FTPS or SFTP) and if GoDaddy disallows FTP access, you're kinda hosed. There is a program
called BitVice
https://www.bitvise.com/ftp-bridge that can act as an FTP server to GRLevel3 and use SFTP to talk to the website. Also complicated to set up but doable.
XFinity doesn't care about http/https/ftp/sftp per se.. they just transport stuff back and forth using TCP/IP.
I hope this helps...