Using Round Corner

Hello everyone, I downloaded the plugin rounded corner but am having trouble using it. When I click the rounded corner and try to pick and edge, it tells me Invalid (group or component). can someone explain this to me?

Thank you

You need to open the group for editing first. The tool doesn’t work from outside, only on the raw geometry.
Open the group/component before selecting the tool.

Having same problem. esp with fillets on two intersecting curved surfaces (viz; intersection of two rods of differing diameters). Have exploded both rods and still “invalid line” comes up. two surfaces not four? permitted /not permitted ??. We need a more detailed what is not tutorial on this plugin…

Upload your SKP file so we can see what you have.