DIAGNOSIS The most likely cause is a clogged or slow-filling water inlet valve screen, restricting flow.
FIX Turn off both hot and cold water supply valves behind the washer. Disconnect the fill hoses from the back of the machine. Use needle-nose pliers to gently pull out the small cylindrical filter screens from the valve inlet ports. Clean them under running water to remove mineral deposits.
IF THAT DIDN'T WORK The water inlet valve solenoid itself could be failing and not opening fully. Also, check that your household water pressure is adequate—other faucets should run strong.
HEADS UP This model uses a lot of water on the Deep Water setting. If you're consistently seeing low water, it's almost always an incoming water issue (valve, screen, pressure) rather than the washer's internal programming.