Hello! I'm sorry to hear that you're having trouble with Microsoft Defender's real-time protection being turned off and not turning back on. If you're receiving a message saying that you are using another antivirus provider, it's possible that the other antivirus software on your system is conflicting with Microsoft Defender.
Here are a few steps you can try to resolve this issue:
1. Uninstall Other Antivirus Software: Make sure to completely uninstall any other antivirus software on your system. Sometimes having multiple antivirus programs can cause conflicts. You mentioned trying to uninstall Smadav USB Protection, but if there are other antivirus programs installed, remove those as well.
2. Restart Your Computer: After uninstalling any conflicting antivirus software, restart your computer to ensure that the changes take effect.
3. Check Windows Security Settings: Open Windows Security by clicking on the shield icon in the taskbar notification area, then go to Virus & threat protection > Manage settings. Ensure that Real-time protection is turned on.
4. Check Group Policy Settings: If you're on Windows Pro or Enterprise, there could be group policies preventing Windows Defender from running. Type gpedit.msc in the Windows search bar and navigate to Computer Configuration > Administrative Templates > Windows Components > Windows Defender Antivirus. Check if there are any policies that might be preventing real-time protection.
5. Run the Windows Security Troubleshooter: You can run the Windows Security Troubleshooter to automatically detect and fix issues with Windows Defender. Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters, then select Windows Security and run the troubleshooter.
6. Update Windows: Ensure that your Windows operating system is up to date by going to Settings > Update & Security > Windows Update and checking for updates.
If after trying these steps Microsoft Defender's real-time protection is still not turning on, you may need to consider further troubleshooting or contacting Microsoft Support for additional assistance.