4000$ is a big amount and this issue should be addressed immediately. If the situation remains like this for next few days, you should open a scam accusation against bitvest, so everyone should be cautious in depositing in this site.
He already opened a thread
Refusing to pay about $4000 in winnings on bitvest.io. he promised to comeback revise the thread and upload all the proofs, unfortunately it's been two days and the thread is not yet revised we have no idea if the accusation is legit and serious, until we see all his proofs, this allegation is just hearsay.