D-Link AC1750 User Manual page 126

Section 4 - Security
5. Enter the same security key or passphrase that is on your router and
click Connect. You can also connect by pushing the WPS button on
the router.
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 121