I know this will probably elicit a few smirks, but I can’t figure out how to select edges to apply fillets to. For some reason, I can’t find the correct tool or key combo to get the job done. Maybe it’s a machine problem. I’ve not found any tutorials that readily explaining this fundamental task.
I will infer that you are trying use the FilletEdge command?
In this case the command works on Joined edges.
The FilletSrf command works on two unjoined surfaces.
So, if you draw a box, you can use FilletEdge. If you Explode the box into 6 surfaces, FilletEdge won’t work because the surface edges are no longer Joined together.
Welcome to the herd
I got to this response just now and I’ve since figured out the distinction. I think.