This is a known issue with macOS Ventura where Full Disk Access is granted but Avira Security still prompts that it is not. This issue has been reported to Apple and is being worked on.
In the meantime, do the following to fix the issue:
1. Choose the Apple menu at the top of your screen, then System Preferences.
2. Go to Privacy & Security.
3. Click Full Disc Access.
4. From the list of applications, select Avira Scan Service.
5. Click - (minus) to remove "Avira Scan Service" from the list.
6. Click < (Back), and then click Full Disk Access again.
7. “Avira Scan Service” should reappear now. Enable it.