Be sure to use the latest firmware for your printer type.
FLsun QQ (8-bit)
You can recognise this printer because it has a power switch to the front, left of the screen. If you have the power button on the front right of the screen or on the rear, next to the power lead, you have a QQS (32-bit) unit, which is different firmware.
Download the firmware. Extract the Zip to the root of an SC card. Insert in to your unit and switch it on. The firmware will automatically install and takes just a few minutes. Do not power off until complete. There is also a video embedded in to this file to demonstrate.
1Mb Zip file
FLsun QQ firmware (Levelling Plate version)
1Mb Zip file
FLsun QQ firmware (Levelling Switch version)