A dishwasher that starts but does not take in water may have a closed supply valve, kinked hose, door that is not confirming closed, a stuck float, or a failed inlet valve. Before taking anything apart, listen to what happens at startup and check supply, door, and user-accessible parts with the appliance off.
Confirm the water valve is open and the hose is not kinked
A valve under the sink commonly supplies the dishwasher. Make sure it was not left closed after other work and that the visible hose is not crushed. If that connection is leaking, shut the water off and correct the leak before proceeding.
Make sure the door latches and the cycle actually starts
A latch that does not confirm closure can prevent filling and washing. Remove items blocking the door and listen for a brief drain before filling, which is normal on many models. An illuminated control panel does not prove the sequence has started.
Inspect the float only if it is accessible from the tub
Some dishwashers have a visible float that must move freely to indicate water level. With the appliance off, clear debris around it without dismantling wiring. A float stuck in the raised position can make the machine think it is already full.
An inlet valve or internal control fault requires service
If water is available, the door latches, and the float is free but no water enters, an electric inlet valve, wiring, or control board may be at fault. Do not apply live voltage directly to components for testing; shut off water and power before service.