Hi Joe, thank you for providing all of this additional information.
Can you check to see if your computer's location settings and the time is correct. Make sure your computer is not on proxy or VPN.
I know you have already done the dns flush and all that fun stuff, have you simply tried the reset network from Settings? Also, is your IP set to auto assignment or did you assign specific IP?
As for antivirus/firewall - are you using third party or built in Windows'? If you are using third party, please uninstall all, instead of just disabling. For example, McAfee, is known to have more than one installed. Besides its security app, it also has web security. So make sure all are uninstalled. Then restart and see if it works.
If it doesn't work still, I am afraid you will want to consider creating another local user and see if it works on the other user profile. Or try clean boot (https://support.microsoft.com/en-us/topic/how-t...) to see if the issue can be due to any third party app conflict. etc.