No Lava in my Pressure Cooked Lava Cake! I tried a youtube recipe for making lava cake in a pressure cooker. It really turned out very good except there was no lava, just cake. I think it was because I over cooked it. I'm not really sure. I preheated the water and then proceeded to pressure cook. I only pressure cooked for 5 minutes because it took 5-10 minutes to build the pressure.
For lava cake, cooked using any method, there is a relatively fine line between perfect and over cooked.  It appears that you crossed that line.