It seems that /spawnmob cow at heights doesn't work - town flags are set to true for mob spawning. possible height was 256. Town: Endor, owners: Celo747, Endoric
if you mean above layer 256. That is supposed to be like that. 256 is the height LIMIT and you cannot do anything higher than that,
What you have to do is place a block then put the cross hairs on the side of the block then type the /spawnmob command, I had the same problem
