Why did my torch-down roof patch fail?
The 1 lb tank will not supply the flow needed. you used the equivalent of a small hand torch with that bottle adapter to the 1 lb tank. There is a smaller than 5 gallon 20 lb tank I think it is 10 lb and will supply the proper flow of propane if you don’t have or want the standard size tank but need a few minutes of high flow. This is the most likely cause but the low temp and wind added or even compounded the problem. Hot tar can be an art but it’s easy to learn.
Getting the surface to be bonded hot enough to “wet” or turn the material surface to liquid then start sticking it down and continuing working it until sealed. With small patches I usually will add tar around the hole or in the area. I have seen guys step on the hot tar to smush it together but I was taught to use a roller so the tar is not smushed out in one spot next to a spot that is not smushed the roller helps for an even pressure, for a small patch the back of a garden rake works. And at last resort light pressure from the ball of your foot not full pressure and make sure to overlap but remember you only have 10-30 seconds depending on how warm you got everything. If you don’t have 10 seconds you are not heating the original surface enough.