Hi Mark,
No, the source field, "Department", is just a simple text field.
Not sure if it is the same root cause, but I just had an issue where I was trying to change my shared field, and it would simply not recognize my choice. No matter if I changed to 'From List' or even selected a different shared field, it was somehow 'stuck' thinking I still had my old shared field selected.
I worked with customer support, and they went in and had no issue with it. I went back in and it was suddenly just fine (of course, customer support thought I was crazy lol). I'm not sure if it was a caching issue or what? My guess was the simple act of some other admin opening it and saving it somehow corrected the issue. Do you have a second admin that can try to edit the field and save it?
If not, maybe try customer support to see why the button is grayed out.
Qrew Legend... or maybe just delete that field and make a new field from scratch.
