Attempt to Auto-fill Form makes field disappear in form view

[mklein]

I am creating a real estate app and working on a function to send property information to a client. To do this, I have created an action where the user presses the button "Send to Client" on the property page and that takes them to a form to capture the client's email, which sets off a automation workflow where an email is sent with the property information. Here is my first dilemma:

I have the address as a ref row to the Property data set. This results in a drop-down field in my "Send to Client" form (see below). I would prefer for the address of the property they were viewing to auto-populate in that field and they simply need to input the client's email. 

When I try to input an expression in the Address field in the Auto-Compute section within the App Formula field, it makes the Address field on the form disappear instead of auto-filling. See below:

Does anyone have a solution? It seems that any expression that I try in that field results in the Address field in my form to disappear. Is it because it is a reference column?