You haven't shared a lot more details that could help us figure out what happened. Please use the scam report format to guide you.

How long ago did you attempt to make a withdrawal?
Bitvest's Founder has been under the spotlight in the last few days for being absent/Offline and not paying signature participants for almost 10 weeks. They say he was apparently sick, but no one knows for sure.

He came back and paid the participants all the 10 weeks today, Maybe you should try sending him a PM about your issue.