@Марвин_С Oh, I'm sorry, I forgot. The connection is established using the Internet distributed by the router, not via 4G or anything else.

@Марвин_С I downloaded the latest version of Thether that was available on Google Play. Version 4.6.14. I am currently using a Red Majic 6R phone and there is only one OS, the native one, version 4.0...

@Marvin_S Update: I just tried to log in to the Tether app. At the entrance, I was asked to re-enter my account (email and password), lol, what the hell. I logged in. I clicked on the icon of my C64...

@Marvin_S Congratulations! If it would make you feel better, I can write you the problem in English, just let me know. I'm using the original TP-Link C64 cable, I should mention. And I have no idea...