Are you a comcast/xfinity customer? That's giving us fits.
Some combination of the following might work.. it has for others.
1) Turning off protected browsing.
To disable this setting, go to the XFINITY xFi app or xfinity.com/myxfi and navigate to Advanced Settings then Protected Browsing."
2) Turning off 'Xfinity HotSpot'
3) Someone did this: Xfinity has an instruction on how to disable it. 1) Need to sign in to your xfinity account. 2) Select xfinity xFi from your services . 3) On next screen select 'More' on the upper right hand corner of the screen. 4) Next screen shows More Options, select 'My services'. 5) the next screen will give you the option to turn off /on Advanced Security.
Thank you all for your help. The Xfinity fix didn't solve the problem, but it gave me an idea, i turned off the McAffee fire wall and voila, I was able to install the 2020 basis version