We just pushed a fix to the issue checker that wasn’t showing some errors. What this error means is that from where you’re using this expression, this element cannot be ‘seen’. For instance, if you have an input ‘Input A’ in a repeating group, and from the outside try to refer ‘Input A’, Bubble will not be able to figure out which input to look at, as there will be more than one. If you are in the same cell the expression would be able to see it
In general, you can’t build expressions with elements that cannot be seen, but if you drag the element outside of the cell.
What I recommend is going through these 23 expressions and confirm you can build the expression with the options in the dropdown.