This is usually because the remote computer is not fully set up for unattended remote access. On the remote computer go to 'Extras' - 'Options' - 'Advanced' - and scroll down to 'advanced settings for connections to this computer' and set 'Access control' to 'Full Access'. After all you have given the password to anyone who logs in so why not give them the access.
The cause of the problem is that the remote computer gets a message which asks if it is OK to grant full access. If no one accepts this question within 20 seconds it declines the connection with the error code 'WaitForConnectFailed'.