Pro Res footage not conforming from Cinema tools

Hi There.

I recently shot some 50p footage on a Sony A7s.

I have converted the XAVC-S files into Apple ProRes using Edit Ready.

But I can't conform any of the clips in order to make them slomo.

I can see that they are 50fps in FCP, but either when I open the clip into CT directly, or via FCP the conform button is greyed out.

Why is this, when it is ProRes footage?

Thank you for any help!

Phil