@Sunshine Creating a new profile solved the problem, thank you very much.

@Sunshine Changing dns did not solve the problem. The ISP of SIM card inside the MR6400is Kyivstar. About a month ago the MR6400 was still working fine with Xiaomi phones.

My Xiaomi Redmi Note 8 Pro tethers with the router, but has problems accessing the internet. I have checked other devices for this problem. All xiaomi smartphones tested had the same problem. But...