Conditions says field is missing but it is not

Hi, I'm having trouble creating a Show/Hide condition.

It says that "Gray (disabled) fields cannot be used as a condition trigger point". When I click save, there's an error message in red saying that the field is missing/deleted. 

But the field I've chosen is neither disabled nor deleted.

This is an existing form and we haven't made any changes for a while. I'm not sure what's happened.

You can just ignore that pop-up. It is just a notification or a reminder that you cannot use a disabled field as the trigger point. Upon checking, I can see that the "Country" field is not greyed out.

To fix the issue, you need to remove the option 1, option 2 and option 3 in the Options box. You can do that in the Dropdown Properties. Just change the "Predefined Options" to "None" and then remove the Options. After that, put the "Predefined Options" back to "Countries".

Here's the result:

Hope that helps. Thank you.