Why does this paint (or stain, or whatever) not want to stick to my fence?
Possible issues include, but are not limited to, the fence is not clean, the paint is not stirred well, and/or the paint has expired.

If you are having trouble getting the paint to stick to the fence, the problem is likely due to a dirty/moldy fence. If the paint seems thin, keep stirring the paint (most of the pigment has probably settled to the bottom).