Hi Tony and thanks for the question there may be several reasons why this could be happening-- which part of the USA are you? and could you send me a picture of the existing concrete? if you can send it to
david@supremeresurfacing.com.au.
When you say stamped concrete do you mean a slate finish ?
How long after the clean down did you seal the concrete?
Are you using a solvent or water based seal?
Ok let me know the above info and a pic if you could
Cheers
David