Generally, a certificate of achievement implies that you have taken a test of some kind. The next thing to find out is where you are trying to get work and what criteria they have for certification and licensing.
If you have a certificate of achievement, what that tells me is that you may/or may have not completed a training program in massage therapy in your state. And, that you probably didn’t graduate, otherwise your instructors would have walked you through the process of state licensing. You probably took a continuing education course by an NCBTMB approved provider and are trying to get your state hourly requirement fulfilled without having to rely on your school.
That’s OK. It can be done, and sometimes the only recourse to someone that was slammed by an unscrupulous school. Check with your state authorities to see what they will accept so that you can get your license.