Whenever chemicals don't do what you expect, it always casts doubt on your test results. Some pH test methods are inaccurate at high chlorine levels. A pool store test would be a good sanity test right now.

A good way to figure out what's going on is to take a 5 gallon bucket of pool water and experiment. A cup of borax ought to make a big difference in the pH of that bucket of water. If it doesn't, try it again with tap water. That ought to give you an idea of what is happening.