If you are unable to withdraw your cryptocurrency balances from Kraken, there may be several reasons for this.
You may see a "Balance is insufficient for a withdrawal" error, or the withdrawal page may say that your funds are "Withheld" or that withdrawals are blocked.
Check the following:
Do you have any orders open/pending? Digital assets/cryptocurrencies that are used in an open/pending order cannot be withdrawn.
Solution: cancel the open orders.
Open margin positions
Do you have any open margin positions? Margin positions require collateral, and that collateral cannot be withdrawn while the positions are open.
Solution: close the open margin positions.
Do you have a negative balance in any fiat currency or digital asset/cryptocurrency? This will prevent digital assets/cryptocurrencies withdrawals from your account.
Solution: deposit funds in the fiat currency or digital asset/cryptocurrency that has a negative balance, or exchange other fiat currencies or digital assets/cryptocurrencies to make up for the negative balance.
Currency not held in your account
Do you have the digital asset/cryptocurrency available in your Kraken account? Although you may see the total amount held in your account, you may have it selected where your account shows the total sum of all of your currencies shown in a specific currency, though all of your digital assets/cryptocurrencies and fiat currencies held are treated separately.
An example is if you hold both Bitcoin (XBT) and Ethereum (ETH) in your account, you can't withdraw the total amount in one Litecoin (LTC) withdrawal.
Solution: exchange your balances to the currency you want to withdraw.
Recent Fiat Deposits
Have you deposited fiat recently? This will result in any withdrawals on your account up to 100% of the deposit amount being blocked.
Solution: try to withdraw a smaller amount or wait 72 hours.