If you change the password on one of your accounts (eg WWE Network, Impact, NJPW etc), you may no longer be able to start any new downloads. 
To fix this, click File in the LetMeAtIt menu and select 'Reset Plugin Credentials'. The next download will prompt you for your new details and then you can continue.

If you change your LMAI account password, you can reset your LMAI account data by going to the Account menu and picking 'Reset Local Account Data'