Trying to Fillet this corner

Hello everyone. I'm trying to make a fillet of a unit of 6 facing upwards, but it wouldn't let me even though I already made a fillet of 6 units on the other edge facing downwards. How would I fillet this edge 6 units upwards? Thank you.

The vertical surface is probably not broken at the horizontal surface. In other words, you are trying to fillet an edge to the middle of a surface. Can't do that. Fillet only works at two ends.

The back of the lower portion cannot be the same surface as the front of the upper portion.

Also, the circle may be closer than 6 units to the horizontal surface.

It looks like you are trying to create a 3DFillet spanning between a 3D Solid and 2D linework.

You could quite easily create the 3D Solid, by drawing it in one of your end or side views as a 2D drawing, then use the EXTRUDE or PRESSPULL command to convert that 2D linework into a 3D Solid.

If you are trying to create a 3D Solid, and using the EXTRUDE command, make sure that your linework is a CLOSED polyline.

PRESSPULL is much more forgiving, and does not require that the linework be closed to generate a 3D Solid.

The following link http://www.cadtutor.net/tutorials/autocad/extrude-and-press-pull/ from the Tutorials page would likely help you a lot, and very quickly show you the ropes.

This is the figure I'm trying to draw for this exercise. There has to be a way to make that fillet.

As Dadgad has pointed out, it appears that you are trying to fillet between a 3D solid and some 2D entities. That's not going to work. Create the 3D solid and then do the filleting. That way, placing your holes will be much easier because you will be working on surfaces with edges you can use for positioning.

This is the figure I'm trying to draw for this exercise. There has to be a way to make that fillet.

I modeled the bulk of this exercise, to show you the process I described in my earlier post, which entailed doing the line work as a closed polyline, which I then filleted.

It would have been quite simple to draw it with the arcs, but you seemed inclined towards using the fillet command, so I did it this way.

Then I extruded the closed and filleted polyline by 40, which gave me a 3D Solid. I 3D Rotated the 3D Solid, then chose an isometric perspective, in which I filleted the 20 radius section at the top.

All that remains to be done is to position and bore the holes which could be done in any number of ways, INCLUDING the SUBTRACT command, or PRESSPULL.

I trust you will be able to figure out one of those approaches.

I would suggest using 2D Wireframe as you do this exercise, it makes it much easier.

I only switched to X-RAY visual style after the fact, for display purposes.