Why won't my 4 Ingredient Toffee recipe harden? It was white instead of a tan color? This beginner needs help, what did I do wrong?

I'm sorry your first try didn't work our very well because the 4 Ingredient Toffee is so good!  Your comments about color and consistency lead me to believe the mixture was not cooked long enough.  Did you use a candy thermometer and/or the cold water test?  Either is key to great candy results.  See Candy, How to Test for Doneness to give you an idea of differences to look for at different candy temperatures.  If you don't have a candy thermometer, start using the COLD water test a couple minutes before the noted amount of cooking time, since stovetops, heating elements and saucepan thicknesses vary.  Also watch the color of the mixture; once it starts turning tan, it can get to the burn stage quickly if you're not careful.  If you did use a candy thermometer, there's a chance it may not be accurate.  Check the temp by placing it in boiling water, which should read 212 degrees at sea level.  If it's higher or lower, make that same adjustment when making the candy (ex., if it reads 210 in boiling water, then cook the candy to 298 degrees).  Or, maybe it's just time to get a new one - good luck with your next try!