Well, since that doesn't help, then a reset outside working hours would do, but this time be careful setting the password.

You may have done that with Caps Lock button ON, while changing the password. Try to reproduce that and see if you can log in again with Caps Lock ON (presuming you don't have any additional alphabet...

@BalicaAdrian These are the setting on your C6 In operation mode section: In network section: Just make sure that cable connection between ISP modem and Archer C6 is : LAN port of ISP modem =>...

Yes, you would be able to have wired/wireless internet via C6 in AP mode, just follow the link I sent: https://www.tp-link.com/ae/support/faq/2066/

If the ISP modem is in router mode, I would suggest you to set your C6 router in AP mode with a static IP LAN address. That way you can avoid the double NAT in your network and extend its wireless...

What mode your C6 is working in ? Router or Access point ?