D-Link AC750 User Manual page 97

Section 4 - Security
5. Enter the same security key or passphrase (Wi-Fi password) 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 GO-RT-AC750 User Manual 93