D-Link AC1750 User Manual page 133

Section 5 - Connecting to a Wireless Network
3. Enter the same security key or passphrase that is on your router and
click Connect.
It may take 20-30 seconds to connect to the wireless network. If the
connection fails, please verify that the security settings are correct. The
key or passphrase must be exactly the same as on the wireless router.
D-Link DIR-868L User Manual 128