Hmmm... Do you have the pink seed for sure? I am pretty sure this pot requires a different seed, though, I can be wrong... Try getting the seed in the vending machine/secret wall seed and see if those work! Otherwise, if you've used the seed in the very first versions of the game, you'd need to delete/edit the savefile (to put "1" next to all Seeds), because I swapped their places around, so the savefile doesn't carry over to new versions very well!