@Fernandoalp Hello,
For ' it keeps rebooting constantly' do you mean WPA7510 is in loop reboot ? may I know how did the Leds change at that time on the extender?
It is recommended to try a different power socket and try factory reset again:
With powerline extender powered on, use a pin to push the reset hole until all the Leds flash once.
Can you connect to WPA7510 default WiFi SSID and try to login its Web :
Please log in web interface of powerline unit by following instruction:
https://www.tp-link.com/en/support/faq/1417/
If power line default WiFi / SSID keeps show up and disappear soon after, sorry to tell you this unit could be faulty on the hardware, you could contact local support or later retailer to check warranty with forum details.