I have many cracks around my window frames. I have used a couple of times Masonry sealant and caulking, but the cracks still exist. I have a can of Flex Seal Clear which is unopened. Can anyone tell me what product may be best for cracks in the cement around the window frames. I live in a warm climate. Thanks

Polyurethane or silicone caulk. If you have a masonry house and vinyl windows, it will always be a battle because the expansion rates are very different and the caulking seal is easily broken.