How to chamfer edge of a hole

Hi this may be a very simple question but I am trying to chamfer the edge indicated with red in the screenshot and it doesn’t seem to work. I am using the chamferEdge command but when it asks me to select edges to chamfer it just won’t let me select that edge. I am able to chamfer the edge indicated with green so I don’t understand why this is happening. I encounter the same problem with the filletEdge command. Any suggestions?

Have you checked the solid is a closed polysurface?

Dosyayı gönderin bakalım.

Ah! Thank you so much! Yeah it was an open polysurface so there was no inner surface to the hole. Sorry a bit silly!

Dear @Lena_Westerburg_Burr please mark David s post as solution.
There is a checkbox below the post - so others don t need to dig into the topic just to see it s already solved. thanks. happy modelling- tom