I got mail from Gmail saying someone from a certain IP tried to log-in and it was prevented and that I should reset my password by following the given link if I don't recognize the address.
"...We prevented the sign-in attempt in case this was a hijacker trying to access your account..."
However, this is not from a hijacker but from an application I set up some time ago. Now it can not access my account. How can I remove the prevention of the sign-in?