I'm seeing a lot of bad advice floating in this thread ...or perhaps advice that doesn't always gel with every industry.

I am in field where a masters degree can fulfill the requirements for greater pay/advancement. How I would recommend approaching it is talking to your boss (maybe CEO maybe not), about your future in the company. I'm assuming if you did a masters while working they signed off and approved of you taking that action.

So I would probably approach a conversation like.

Hey I went back to school and learned x y z skills, I did that in hopes of taking a greater role in a, b, c process. What is the future of a, b, c role in terms of who will be working on it and from what position. See if people are receptive to you expanding your responsibilities and then figure out the pay conversation from there.

You very well may have to change firms or apply internally for a new position in the company, but take it from the approach of you actualizing the new skills that you have. Most companies understand that if you do more important and harder work you will be compensated accordingly.