@Aszz Hello, 

You could forget the Wi-Fi network on cell phone and see if you could reconnect to WiFi. 
Go to Settings-> WiFi on your phone, Tap (or Long press  the router's WiFi name  ->Forget / Delete the network 

Can you help check the back or bottom label and found the exact model number and its hardware version?

https://www.tp-link.com/search/?q=ac750&t=product&p=1

How about the Led status on tp-link, and what is the Error message if phone failed to connect to WiFI?