Tried the reset button twice but amber light still flashing
That's not a factory reset.
I'm a great believer in the KISS principle.
Configuration is simple if you start from a factory default condition. Then connect the Airport to AC power and finally to the Internet modem (or modem/router). Open Airport Utility on your Mac or other computer and accept all of the recommendations. After confirming that it works, insert your desired administrative and WiFi passwords.
Do not expect the Airport to respond instantly to the configuration commands. BE PATIENT!