Secure link failed

Please please please can someone put me out of my misery and help me to fix this issue?!

I have windows 10 (laptop) and Norton 360 premier and the latest version of iTunes.

Half of my iTunes library is greyed and "waiting for download", when I try to update my icloud library it looks likes its connecting, tells me it's waiting for apple to download my music and then cuts out with no changes taking place in my library.

Run iTunes diagnostics and this tells me "secure link to iTunes store failed".

I have spoken to Apple on numerous times and they all say they've never heard of this issue (clearly they've never goggled this because I've found hundreds of complaints about this!), I have been told to: re-install iPod software via iTunes (can't do this because it wont connect to the store so tells me the download will take 30+ hours and then stops working), reset iPod to factory settings, re-install iTunes, turn off windows firewall/Norton.

I have done all of this as well as the netsh winsock reset and nothing works.

I am beginning to get REALLY agitated about this issue!!!!