I seem to have a problem using the Mirror Geometry action, you see, when I mirror the object it leaves edges non-merged and I can´t play with them, delete them, nor anything.

I made the same procedure with a single cube, subdivided it and made the whole process even using the same settings and it worked, I could even delete the edge and leave the face. But I can´t in my model.

What could be causing my problem?

Thanks for any feedback.