What is your operating system and firewall ?
Does it allow avastSvc.exe internet access ?

  • If it does delete the entry for it and do a manual update and reconnect to the internet, this should force the firewall to ask permission again.

What version of avast dis you have before ?

Was this a clean install (removal of previous version) of 8.0.1497 or a program update from the avast UI ?

NOTE: Having two resident AVs installed even if one is disabled can still cause issues, disabling one AV doesn’t unload or stop its drivers and these can conflict.