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 Digital assets/cryptocurrencies that are used in an open/pending order cannot be withdrawn.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 spot positions on margin
Do you have any open spot positions on margin? Opening spot positions on margin requires collateral, and that collateral (including any assets you received from the market when you opened the spot positions on margin) cannot be withdrawn while the positions are open.
Solution: settle or otherwise close your open spot positions on margin.
Do you have a negative balance in any currency? This will prevent withdrawals from your account.
Solution: deposit funds in the currency that has a negative balance, or exchange other currencies to make up for the negative balance.
Currency not held in your account
Do you have the value of the particular asset(s) you are looking to withdraw available in your Kraken account? You might see the total account value held in your account displaying under one default currency, but this could be a combination of several different assets, which you are only able to withdraw individually.
An example is if you hold both Bitcoin (BTC) 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 recently deposited fiat for the first time? 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.