Ultra Combo Customization

Vantage 8.03.305L

I have added a Ultra Combo Drop-Down. I have walked through the steps
to retrieve the list I want. After saving my work, and before closing
out of the customization window, I check the drop-down list and
everything appears ok. I exit out of the customization screen and
launch the form. My customization is there but it is not active <I
cannot access the list>. It is grayed out.

I am pretty new to customization. Anything I may be overlooking?