Jen Kuntz looks at the dreaded Object reference not set to an instance of an object error in the context of GP and SmartConnect. Nothing like a recursive sounding error message that tells you a little bit about nothing to get the day started right. Check out Jen’s post atjenkuntz.ca/2019/04/object-reference-not-set-to-an-instance-of-an-object/
Object reference not set to an instance of an object – JenKuntz.ca
Archived post from 2019. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.