@Haybabygirl 

Hello, if you have changed the router and need to connect the extender to a new router Wi-Fi, please reset the extender into default settings again by holding the reset button until all lights flashing once, then refer to this instruction to configure your range extender again carefully:

Via Tether App: https://www.tp-link.com/support/faq/1373/
Via Web interface: https://www.tp-link.com/support/faq/1400/