The program tries to log you in with your supplied password. Google has enabled higher security by default now, so when the program tries to connect with the password you supplied, Google will deny the login attempt even though your password may be correct requesting that you authorize the program to have access to your Google mail account.
Because Google denied the login even with the right password, you would receive a Google denied login email notification the first time. You can ignore this provided you follow through with the prompts from the program as described below.
More info about security