Having issues with drop downs and grouping

I made a workbook about 3 years ago, and don't remember some of what I did here. Pretty sure I did receive help here though, when I first made it, so I'm trying again.

On a second tab where all my 'info' is, I have a table with headers. On that tab, the headers on columns D-I are grouped as 'Shop'. On the main tab, I can select a shop by name in a drop down that's in cell D1, and via the INDIRECT function, a second drop down in B3 shows only the staff names that are in the same column within the same table on the 'info tab' as whichever shop I selected. My issue now, is we have new shops, and I have added 3 more columns to the table, but the second drop down (B3) on the main tab won't let me click on the arrow for the drop down, when any of the new headers are selected in D1. The originals still work as intended. I can't change the group 'Shop', as any time I try to ungroup it, I get an error saying I cannot ungroup it, and Shop was the source for data in D1. So, I just selected all 9 table headers for source in the data validation window instead. I don't know if the group is what's making the drop down un-selectable or not.

Any help or suggestions would be greatly appreciated!