Note: For the keyword "allwinner t5 firmware update full", you will strictly be looking for the raw .img file format. Step 1: Prerequisites and Required Tools
This indicates a driver issue or a bad cable. Reinstall the Allwinner USB drivers, try a different USB port (preferably a USB 2.0 port on the back of the motherboard), and verify you are using the designated USB-OTG port on the T5 device. allwinner t5 firmware update full