This is almost certainly due to an incorrect passphrase. Following the BIP39 specification, Whirlpool stores nothing in your wallet file that is derived from your passphrase. This makes a passphrase enabled wallet more difficult to brute force. It also means that if you enter an incorrect passphrase, Whirlpool will be using a different seed and will therefore derive different addresses. Your existing address labels will even be applied to the new addresses, since Whirlpool has no way of telling the passphrase has changed. Further, your wallet will show no funds are present. They are not lost however.