Did you put air in the tire after you put in the 'punture seal'? If not, pump that bad boy up! If you did you may have a problem with the valve stem. (could be your leak).
For future reference (I know you said that you are putting on new rims and tires) NEVER USE 'PUNTURE SEAL'! You will NEVER be able to properly balance that tire, again. What happens is the sealant dries on the tire and causes the weight distribution to be thrown off. Even if you get it rebalanced...you may still feel a vibration. That stuff just make a huge mess and makes it difficult to repair the tire.