So far I have been unable to find any reason at all for this problem
Lets reset Avast
Download Avast Uninstall Utility to your Desktop.
Download the correct version of Avast
Avast Free
Avast Pro
Avast Internet Security
Avast Premier
Disconnect from the net
Uninstall Avast via control panel
[]Run the uninstall tool and accept the reboot to safe mode
[]Once complete reboot your system
[*]Reinstall Avast
Have reinstalled Avast - but need an activation code! I don’t have this! ???
What version os it ? I.e. Free, pro, ais ?
If free then just register again
If paid for then https://www.avast.com/en-gb/resend-license-paid.php
Have had a my license resent - but cannot open it. not sure what to do?
There is no need to open the licence
Copy the licence to your desktop and double click it, allow Avast to insert it
Ok, thank you. all is done. I tried the website whilst I didn’t have Avast - it worked fine. Now I have Avast back - it doesn’t! 
Do you have AIS ?
yes
All I can think of now is to remove all rules within AIS firewall
Tools > Firewall > Application rules
Then set the default action to ask
Tools > Firewall > Settings > Policies