Just to clarify, i started trying the game again and i just tried and i was able to buy a tower above the Advanced Cannon, i bougth and Extreme Cannon. Im on Wave 30. What was the tower you can not buy or the game wont register?
Yeah yesterday i bought the Extreme Cannon but i think it wasnt doing damage it said "DPS 0" but now after closing the game and opening it up again and selling every tower i tried building one Extreme Cannon and one Lazorz X tower and they both work. It may be a bug after buying too many towers/upgrades and you need to re open the game or sell towers.