After evolving my Slowpoke into Slowking, I attempted to level it up. After knocking out a few Pokemon I realized it wasn't gaining any Exp. It happened after Slowpokes evolution into Slowking 11/2/2017 Server-15 (It says "Growlithe has fainted! Turn over". No Exp was gained.)
Hello Dr. Eximus, The reason slowking is not gaining experience is because it is a generation 2 Pokemon. Gen 2 Pokemon will only gain exp in the Jataro region / Gen 2 world unless hatched from an egg. I hope this helps, if you have any other questions feel free to message me on discord or on the forums!