That first coat cannot and will not cure out with that second coat over it. This would eventualy dry in a warmer time of the year, but coolness and damp nights will take this forever to dry and cure out.
I really would suggest that you contact a local painter that is a reputable painter and seek his/her advice on this. I would think that you would need to use a product from Sherwin Williams called deck wash and brightner by Culprinol. This would strip the deck completely down to the bare wood and then you can hire a professional to stain the deck again with any Culprinol deck stains. The installer must read the instructions carefully and be careful about cool and damp nights. You might want to continue this project next spring or summer when its hotter.