Just pull down from top, you will see an option for usb connection such as charing only or MTP (file transfer). You change to file transfer oftion will solve ur issueI have installed 6.6.12 on my mi4w and want to install 6.6.14, but when i connect device with laptop it does not recognize my device. So not possible to install 6.6.14. Somebody knows how to. Usb connector has changed. No option for transfer data?