Apologies, @poliwiwi. I have overlooked your message. It says that you have not done a factory reset.
We can try to do it to check if it will do the trick, but we'd like to set your expectation that it will return the modem to its factory default settings. If you have customised your Wi-Fi name and password including the modem log in, that will be erased and you may need to reconnect your device to the default Wi-Fi name and use the default password.