Hi Keith,
We regret the inconvenience caused.
In this case, we'd request you to follow the below steps & remove any/all leftover traces of AVG from your Mac;
- Open Finder
- In the menu bar select GO > GO TO FOLDER
- Type: /Library/Application Support/
- Locate and delete AVGAntivirus folder manually (Restart your mac)
After removing the traces & restarting your Mac, please try reinstalling the AVG Antivirus.
Let us know if the issue still persists after performing the above steps.