First of all, to determine what model of your mobile phone, what operating system to use, generally mentioned in the mobile phone manual, you can also find the corresponding instructions on the Internet.
In the power on state:
If it is a non-intelligent system mobile phone, some mobile phones need to manually set the USB data connection in the mobile phone after connecting the data cable, so that the data connection between the mobile phone and the computer can be successfully performed.
Some mobile phones also need to install the management software in the driver CD that comes with the mobile phone beforehand to connect successfully.
If it is a smart system mobile phone, most of them only need to connect the data cable. A small number of mobile phones need to be installed in advance with the management software attached.
3 reasons please exclude
1 computer usb interface power supply is insufficient, resulting in unrecognized, or the driver is not installed or your windows operating system is a lack of necessary components in the lite version.
If there is no problem suddenly, it should not be the operating system.
2 data lines
3 The internal solder joint or looseness of the USB port of the mobile phone leads to poor contact or damage.