Why is the provider's password dir-300 not changing?

Question

System administration

Not an expert at this setting at all. In general, I lived in the same apartment, then moved and changed providers.
I started to make all the necessary settings, when suddenly for some reason the provider's password stopped changing.
Already changed the firmware and set it to default. The router itself is old dlink dir-300 Hardware Version : Bx Firmware Version : 2.06
I suppose that it's not about the software at all, maybe windows 10 jambs?

Answer 1

provider?

Answer 2

Reset from the interface, reset manually, then set a password (ppoe? l2tp?), but configure from explorer, it's better in compatibility mode.