Option A.) Burn off the coating with a torch. This can be dangerous in certain circumstances, so use a small torch (the kind chefs use to make creme brulee).
Option B.) There are specialized products that are made specifically for removing this hydrophobic coating. If you don’t have access to these products, try stove top cleaners.
Option C.) Add more slip solution and make sure that you’re seeing suds on the window. You want it to lather. Use double the normal amount. For example, if you use 2 drops of baby shampoo, increase that to 4 drops. If that doesn’t work, keep increasing the concentration to triple or even quadruple the normal amount of slip solution.
Answer D.) Give the window a good scrub with steel wool, and then reverse scrape by running the scraper backwards only.