The contest holder asked me for revisions but the contest has ended. What can I do?

Revised sounds cannot be submitted to a contest after it has ended.

Explain to the contest holder that they need to call Vinylmint customer support to reopen their contest.

If your sound was declared the winner, any extra work the client needs (beyond small finishing tweaks to that sound) will be conducted for free until the fourth revision, in which each additional revision will incur an additional revision fee.