This looks normal to me. The cylinder with which you started is not solid - it is hollow. So when you round off the edge and then delete the end of the cylinder, you would expect to be left with that rounded edge only. Blender doesn't automatically make hollow objects solid.
I presume you're making something like a mug.
Instead of deleting that end face, pull it down inside the mug to form the inside and bottom.
Alternatively, after deleting that face, select the edge of the remaining cylinder and Extrude it down inside.
Try following Blender Guru's "donut" tutorial in which he does exactly what I describe when creating a coffee cup. You can find it here...