Can't sketch on or edit object

[stevelovellU439C]

I've recently converted a purchased quad mesh to a solid in Fusion 360, I've broken down parts of the model and want to sketch, edit and recreate parts of it. 

Fusion only allows me to sketch on origin planes and I can't choose a flat plane on the body or make any type of edit to the body. I thought it might be a patch issue, but it seems to be manifold. (Not that I really know what I'm looking at within the Patch environment).

I've been working with solids and sketches for months now, but this is really confusing me. Can anyone identify what the problem is? Many thanks.

Here's just one part I'd like to begin with:

https://a360.co/3j8LxPV

[davebYYPCU · Accepted solution]

Fusion does allow sketches on any planar object, 

Your converted object may not be planar.  

If you can’t make a sketch on the ring face/s then you have no planar faces.

Might help...