Connecting to your LinkedIn account is easy. However, sometimes LinkedIn cookies make it difficult to connect another client's account to Octoboard. What happens is when you are trying to enter another client's credentials in the login popup window it closes. This is the same issue for both apps.
This is because you are logged into LinkedIn outside of Octoboard. LinkedIn sees an attempt to login and uses data stored in your local cookies to "speed up" the login process.
To work around this issue, when entering another client's login details, make sure you log out of LinkedIn outside of Octoboard. This will only needs to be done once per clients. Octoboard will remember all logins and start collecting data for all clients without asking for passwords in the future.
This video shows the process of connecting to a 3rd party application.