I've seen this question twice before relating to an offshore cryptocurrency exchange, where they want you to pay "the taxes" before you can withdraw funds. I believe this is a scam, and you will be lucky to get anything back.
In brief, IF a tax payment is required, there is no reason that a legitimate firm can't withhold the payment themselves and send it to the IRS as "backup withholding". This is what every legitimate IRA firm will do, for example, if you request a withdrawal under age 59-1/2; they are required to withhold at least 10%, send it to the IRS, and report it on the 1099-R.
An overseas firm can't generally be bound by US tax laws, unless there is a tax treaty between the US and that country. If there is a tax treaty, they might be required to withhold funds and send it to the IRS on your behalf, and you get credit for that withholding. If there is no tax treaty, they can't be forced to withhold anything, and your payment of taxes is entirely on you and depends on your honesty (and fear of audit, to be honest).
The idea that you need to pay them first, before they will cash out your asset, is a major red flag.
