Disclaimer: Please follow the below at your discretion, as I will not take any responsibility for problems encountered or any damage that could occur. This may also void your warranty. You are flashing at your own risk.
Step 1: Go to Acer Aspire V5-571 support page from here and download the correct BIOS file.
Step 2: Unzip the Acer Aspire V5-571 BIOS file into the root of your FAT32 formatted USB Thumb Drive.
Note: You must format your USB for FAT32, and please note that some Acer bios download files are zip or extractable .exe (Use the smallest USB Thumb Drive you could find).
Step 3: Remove the AC adapter and the battery and hold down the power button for 15 seconds. Release the power button. Plug in the AC adapter and battery.
Step 4: Insert the USB Drive into one of the USB ports on the Acer Aspire V5-571 laptop.
Step 5: Hold ESC & FN key and while holding then press the power button.
Step 6: Keep holding for a few moments until you see data on the screen.
Your laptop should boot again.
If flash the Acer Aspire V5-571 BIOS with USB drive didn’t work flash BIOS with programmer (How to flash BIOS with programmer).