DIAGNOSIS The LED segment display is failing. This is a known weak point, likely due to a poor solder joint on the LED driver circuit or a failing display module itself.
FIX Contact Instant Pot customer support. This is a defect they are aware of. Have your model number (Vortex Plus 6QT) and serial number (on the bottom label) ready. They will likely offer a replacement unit or a repair under warranty if you're within the one-year period.
IF THAT DIDN'T WORK If it's out of warranty, the repair is not user-serviceable. The display is integrated into the main control board. Using a flashlight at an angle might help you temporarily see the dim segments, but the display will continue to degrade.
HEADS UP Don't try to open the unit to fix it yourself. There are no user-serviceable parts inside, and you'll expose live mains voltage components. Tampering voids any remaining warranty and creates a serious shock hazard.