Hi if the low battery indicator is not activated and you have sure to have good new battery without old battery leakage having corroded the contacts the problem seem to be with the LCD display connection. Most LCD display are connected to the device main board without soldering. A data ribbon is pressure inserted into a kind of socket (all this is inside the machine and require disassembly. You need to make sure it is firmly inserted on both end. It often happen with mobile device to be dropped or bumped so that this can internally disconnect just enough to make a display look faded (sometime it is a simple contrast setting but i don't see any in the manual). I assume that because this as a small internal compressor that the vibration eventually made the disconnect. Try to open it (without any DC power of battery to it) and verify the data ribbon insertions (it may be soldered glued on one side but sometime they are free on both side of the ribbon).