My nutone unit will not shut off at the wall inlet

SOURCE: My nutone cv556 wont shut off

It sounds like the relay is bad. This website has a pretty good trouble shooting page.

https://www.centralvacuumstores.com/cvs/trouble_help.php#wont_turn_on

SOURCE: Nutone CV556 Vaccuum Cleaner -Continuously running

Start with this. Unplug the vac to shut off, then disconnect the low voltage wiring at the vac.Plug the vac back in. If the vac still runs you have an internal short on the relay or wiring inside the vac.
If the vac stops then the vac and final wiring is OK and the problem is in the wiring in the house.
Have you removed any inlets for painting or had any renos done or pictures hung. If so undo what you did last. If inlets were disturbed remove them and look for low voltage vac wires touching metal backing plates in the wall or touching the inlet mounting screws.
If you have done a reno or hung pictures you may have pierece the wire for the vac creating a low voltage short which will keep the vac running until removed. I have seen this happen with freshly installed 1/4 round molding along a baseboard

SOURCE: A Nutone CV-450 System with inlet nozzle switch issues

You are suffering a connection problem of the hose end fitting to the wall outlet. Either the hose is not aligned with the two pins in the wall outlet, or the pins in the outlet are dirty and not making good connection to the hose end fittting.