Since can't see how you connected it, you will need to give us a detail description of the connections or pictures.
so like this see where the black is on the second switch.The three black wires are wire tied together. The common coming into the box is tied to the common going to the outlet. The red to the outlet, the red to the other switch, and common to the other switch were hooked on the three way.
The red to the switch goes on the common screw, the black at the other switch goes to that common screw.That is a great diagram. The only struggle I currently have is knowing what is the common on the three way switch’s shown.
Take the black off the outlet and see what happensThat’s exactly how I have it hooked and I still have full hot top and bottom outlets. I have the tab broke off on the red and black side. I will pick up another outlet tomorrow and see if that makes and difference.
Have you mixed up the cables, could it be the other 3 wire going to the outlet.The top outlet went out but the bottom outlet stayed hot.