@woozle I made an effort. However, the router is deemed a "Complex electronic device" under the rules of my country (Russia), and before the vendor can accept it back, it must be inspected by an...

@Joseph-TP I confirm I reset the router as you describe. Though I still do not have the router working, now I have the knowledge - why. After I enter the admin password in the web interface, one of...

@woozle I appreciate the idea. I'll attempt to set up the internet connection and install a firmware upgrade from a smartphone.

Joseph-TP All of this were the first things I tried. Nothing did help.

@woozle No, it does not explicitly reject and does not show any messages. The login page just submits as a normal login process, but then the same login page displays again.

My new router is a TP-Link Archer A5 V6. I attempt to configure the router via the online user interface at http://tplinkwifi.net and/or 192.168.0.1. The router requests a new administrator password...