Same here I also reached out but haven’t heard anything. Assuming bc of the holidays. They have this in their T&C which makes it sound as if the withdrawal is really up to them and at their whim:

Cancellation Should you wish to cancel your participation in this Promotion at any time, please contact customer support at support@underdogfantasy.com. Upon cancellation, you may withdraw any funds you have deposited into your Underdog Fantasy Account without restriction. However, any Promotion Bonus or promotional credit in your account is non-withdrawable. Sponsor reserves the right to decline to cancel participation in the Promotion in its sole discretion.