Thank you Chen!
That did the trick, I had partitioned it GUID Partition Map!
For anyone who finds this in the future... the option to change the Scheme is not available in MacOS unless you choose the View "Show all Devices", then you Erase the top level of the device as opposed to just reformatting the partition... which doesn't allow you to change the Scheme.
I'm now ready to shoot all night again 🙂