Look back over the directions to make sure you didn't miss something. Usually they say only put one drop of the glue on the metal mount surface... that may be enough, but I always make sure there's a little more on there so I'm sure the whole surface is covered.
And if it says press it to the glass and hold it there for 3 minutes before letting go, I usually hold it for 4 minutes.
On mine, it's a little metal pad that I glue to the windscreen... not the whole mirror... and the directions say leave it alone overnight or something before mounting the mirror to it.
2 pages of directions here...
http://www.popularmechanics.com/how_to_central/automotive/1272426.html ...read all of it carefully.
Are your directions similar?
