Hi,
if Norton was running during your upgrade and downgrade then your issue might stem from that. Basically when upgrading security needs to be turned off.
The other thing which might be your issue is Norton itself. Norton used to be a great application (circa 2002) but nowadays it's turned into a many headed monster with it's tentacles wrapped into almost every part of your system. My first recommendation would be to remove Norton using the Norton removal tool:
Uninstall your Norton product using Norton Removal Tool
Just use the onboard Defender for now.
Perhaps a friend will help in downloading of the above tool? If you can use a friends machine to download on then try and grab a copy of the network driver for your machine as...