If I completed my masters could I still apply for green to gold or did I miss out?

Green to Gold is an ROTC program. If you have your masters you really don't need to go to ROTC. If you want to commission you should apply for OCS.

Having a Masters implies that you have a Bachelors. Green to Gold is a commission route for those without. In your case, OCS or Direct Commission (depending on what your degrees are in).

What did you get your masters in? And just like it's already been mentioned, go OCS or look into direct commissions...