Yes, your company and you are obliged to tell PNP if your job situation changes. They might choose to give you a grace period to look for a similar job before they retract your nomination.
But...it has been almost 24 months since CIC received your application. Have you not heard from them at all or is this a delay that you had expected or know the cause of? If you don't know why the delay is, I suggest you call CIC or contact your MP if you reside in Canada. That is not a normal timeline!