- Confirm the URL is
https://dav.lightdrive.one/USERNAME/contacts/with your LightDrive ID in place ofUSERNAME. - Use your full LightDrive email address as the username and a current Contacts-only password from Contacts → Mobile & app connections, or a current Email & contacts password from Settings → Security → App & device access.
- If the app cached an old credential, remove the saved password and enter the correct newly created password when prompted.
- Confirm that the Contacts collection is enabled and the app has contacts and background permissions.
- Check which account owns a missing contact; device-only and third-party contacts are not sent to LightDrive.
- After synchronization completes, confirm the change in the Vault Contacts app and refresh contacts in LightDrive Email.
The main Vault password, Vault app passwords, and Email-only passwords do not work for CardDAV. Do not bypass a certificate warning. If the exact HTTPS address still produces one, stop and contact Support.