Flashing "compatible" firmware from a different A50 device often fails. Users frequently report unbricking attempts being unsuccessful without the exact original ROM image.
💡 : Allwinner A50 is a Cortex-A7 multimedia SoC. Firmware is board-specific — the same SoC can have completely different firmware for different tablets, so a random “A50 firmware” may brick your device if not matched correctly. allwinner a50 firmware link