We had the faux concrete
finish installed 3 1/2 years ago. At the 2 1/2 year point, we started
noticing white areas. The contractor who did the work originally is no
longer in business. We put a water based sealer on at the 3 year
point. It did not help the white areas but just put a light shine on
the finish. It is really looking bad and we want to fix the white areas
which are especially bad near the pool edges. What needs to be done?
Will we have to strip everything and start over?

Yes you will need to strip everything and start over. Typically you will need a stripper that contains "methylene chloride". This is a very strong paint stripper so be very careful around the pool!