Radio buttons - clicking one on turns both on? Easy fix I am sure - but I can't think

I inserted two radio buttons from the developer tools (Form Controls)
I want them to work like radio buttons - you can only choose one or the other. But if you choose one, the both get chosen.

I have inserted radio buttons into other sheets and they work correctly - there is no grouping, I have tried linking the control to the same cell - and then to different cells