trying to set a customer field value on a proposal to '687154 CMS communications' but i keep getting this error: Invalid entity reference key 687154 CMS communications Any idea why? When i paste that string in UI it works fine, it finds a match.

You should be using the internal id in a script

yes i have the internal id of the customer, but when i paste that to the list field it does not find a match. the customer field on a quote is required. and i get an error, please enter customer

In the UI you would enter the customer number. In a script if you use

setValue

you need the internal id. You could probably use

setText

with that but it's not recommended.