LIte Coin Private Key

I have a Lite Coin Core Wallet but can’t get the private key
dumpprivkey with address but I get this error message
Error: Please enter the wallet passphrase with walletpassphrase first. (code -13)

Apparently the wallet is lock and to unlock it you have to put in your phrase and then it unlocks
but this had not worked
until you put like


for the seconds you want it open