My machine lights up but once you shut the door it

That sounds like you are on Pause or Delayed Start. Try Pressing and holding the button. You can also try disconnecting from the mains for 5 minutes.

When in doubt, read the manual :>D

START/PAUSE button with indicator light: starts or temporarily interrupts the wash cycles. N.B. To pause the wash cycle in progress, press this button; the corresponding indicator light will flash orange, while the indicator light for the current wash cycle phase will remain lit in a fixed manner. If the DOOR LOCKED indicator light is switched off, the door may be opened. To start the wash cycle from the point at which it was interrupted, press this button again.

and also

! If the START/PAUSE indicator light (orange) flashes rapidly at the same time as the function indicator light, this indicates a problem has occurred (see "Troubleshooting").

https://manualzz.com/doc/50330217/hotpoint-fdl-9640p-uk-instruction-for-use

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E3 error code indicates here that the washing machine has detected that the door on your washing machine is not shut and that can not start a wash cycle. If the door is shut and the E3 error still keeps on occurring that means the machine is unable to lock the door to begin a wash cycle and requires service to be repaired.

You're start/pause button should pause the cycle, cancell should completely cancell. After pressing the Start/Pause within a cycle, the door lock may require time to unlock as indicated by the lock light on the panel.

Hello Angela Gilmer - Usually when "PAU" displays on the screens, it indicates that the unit thinks that the door is not securely latch when you started the cycle, or the cycle has been interrupted. Try pressing "PAUSE/CANCEL" or "START/PAUSE" once to resume washer. If proves to be ineffective, try reprogramming the unit by unplugging it or flipping the household circuit breaker off. If fault reoccurs, then it typically means that the unit has a faulty door latch. If you aren't certain that the door is properly shut, then the latch assembly may need replacing. Contact a professional to assist with the repairs.

A DE Error Code is indicative of a "Door Error". This indicates that the washing machine door is not shutting, locking or opening

1. Your Maytag Neptune washing machine displays error codes, also called "help codes," to identify specific problems with your washer. Once you close your Maytag Neptune's door, the machine locks the door, goes through the selected wash cycles and unlocks the door when the laundry is finished. Error codes appear when there are problems with the door, the inflow and drainage of water and the motor.
Do
2. Your Maytag Neptune washer displays the "do" help code when the washing machine is trying to start a cycle, but the door is open or not locked properly. If this message is displayed, close the door securely and restart the washing cycle.
FL
3. The "FL" code indicates that the washing machine was unable to lock the door after you closed it. Open and close the door tightly, then restart the washing cycle.
Sd
4. The "Sd" code indicates that you have added too much detergent to the washing machine and your laundry has too many suds. The machine will stop displaying this code if it has successfully run the suds recovery cycle, which removes the excess suds from the wash load. If the code remains, reduce the amount of detergent in the load. Use less detergent for similar loads of laundry in the future.
PF
5. The "PF" code indicates that a power failure has occurred. Restart the wash cycle. If the code still appears, check that the washing machine is still plugged in to the electrical outlet.
Nd
6. The "nd" code indicates that your Maytag Neptune is not draining as it should. Check that the drain hose isn't kinked and that the stand pipe isn't clogged. If you find either of these problems, fix them before restarting the washing cycle.
LO
7. The "LO" code appears when the washing machine has finished the selected wash cycle, but cannot unlock the door. Verify that the door is closed properly, push the "Off" button, and wait two minutes. The door should unlock and the error code will disappear. If the error code remains, unplug the washing machine, wait two minutes and plug it back into the electrical outlet.
Lr
8. The "Lr" code indicates that the washing machine's motor is not running as it should. Have your Maytag Neptune washing machine serviced by a certified Maytag repair professional.
   

i would get a new door or catch from the hotpoint website hope this helps

This usually indicates that the sensor which determines that the door is shut properly could be faulty.

My WMA33 does this occasionally. I manually push the door in and up slightly with my knee - and then start the wash cycle. This seems to work every time.

Failing that you will need to replace the door sensor. A call to hotpoint may help.

Door not shut Check that the door is properly shut.Faulty interlock A faulty interlock might not allow the door to shut properly. Find your door interlock here and replace, or contact a qualified repairer.
No power Check the flex, plug wiring, fuse and mains supply for faults.
Faulty on/off switch Check the power light if fitted. Replace your on/off switch.
Water supply disconnected or off If a washer dryer cannot load water it cannot start a wash cycle. Check water supply.

Maybe that the door is shut "mechanically" but the micro-switch that indicate the control unit that door is shut,is faulty.