Hi salamala, what radius are you trying to use for the fillet?

I tested loading your file and it seems to fillet ok for me over here.... You won't be able to go much above radius 1.2 though, and also it's normal that some partial selection of edges like the one you show above with only 2 edges selected would not work, that would try to open up a hole in the object. The entire ring of 4 edges should be selected in order for this fillet to work.

Here's what I get in v2 when I try it over here:





- Michael