It is possible that sometimes the AVG software fails to detect virus, malware, Trojan and ransom-ware that might create trouble to your device. To fix this glitch, it is advisable to check the configuration settings as the wrong setting will stop the antivirus to scan virus. Also, check your device update permission setting which sometimes blocks the latest version to work due to security reasons. It might be possible that the software is not installed properly after the update. Kindly uninstall it and reinstall to enjoy benefits of this antivirus.
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