When I try to chat, "Signing transaction failed" error message appears.
How can I solve that?
Unlock your wallet.
I can't find unlock button anywhere..

delete your current wallet and create a new one

ps: might think before following this advice
Debug console > walletpassphrase
Thank you.
But I could chat only one time.
Wallet is locked after the first chat

Do I need to unlock my wallet every time when I chat??
set time out to 9999999999, it will be unlocked permanently.
New to this too... trying to understand. So in your example...
walletpassphrase = the password one would use under settings in the GUI to encrypt one's wallet?
foo = passphrase ^^
time out in seconds = length of time in seconds to keep the wallet unlocked ( understand). 9999999999 = indefinitely
walletlock = re-lock wallet
Thanks