● Please change to another OTG cable and then try again.
● Please check whether your HUAWEI Phone P9 supports plugging in a microSD card and a USB flash drive at the same time. If it doesn’t support it, it is recommended that you switch to a different phone, because when you connect another phone to your phone using the OTG cable, your phone sees the other phone as a card reader.
● If you are connecting a USB storage device to your phone using an OTG cable, your phone will provide power to the device. Some USB storage devices that require a lot of power or which your phone cannot provide power to may not work properly.