Since antivirus is the primary culprit, start here.
For Windows Defender specifically:
| Cause | Solution |
|--------|----------|
| Missing/corrupt file | Verify files in Ubisoft Connect |
| Antivirus quarantine | Restore + add exclusion |
| Broken Ubisoft Connect | Reinstall launcher |
| Permission error | Run launcher as Admin |
| Windows corruption | Run sfc /scannow | assassin 39-s creed valhalla uplay r2 loader64.dll
Sometimes loader64.dll fails because the launcher itself is broken. Uninstall Ubisoft Connect (your games will remain), reboot your PC, and reinstall the latest version from Ubisoft’s website. Since antivirus is the primary culprit, start here
