You cannot flash these boxes with a standard charging cable; you need a USB-A to USB-A cable.
This is the most reliable method for "fixing" a bricked or laggy device. Amlogic USB Burning Tool Recovery Guide: Revised Tutorial amlogic s905l2 firmware fixed
Before you attempt to fix your firmware, you need the right tools. Using the wrong software version can permanently brick your device. You cannot flash these boxes with a standard