Trouble cutting on a curve

I am attempting to cut a groove for sealant in a part. I thought this was pretty straightforward, But I cannot figure out how. Every time I do it, It crashes and tells me it is unsolvable. It is pretty simple geometry, I cant figure out why it has issues.

Can a guru look at this thing and tell me what the issue is?

I am looking to take the last sketch in the tree and project it down on to the curved surface and cut a .100 groove in it.