I can create connections for List & Library. I'm getting errors in when using the connection after 30-60 minutes. It creates without an issue, and it works without an issue, until it stops. "Invalid authorization for connection 'List Access'. Credentials may have expired."
We have another connection that is set up with the same account (site & user administration) which uses Basic (username and password). That connection works fine and has never broke yet, just when it's being used in the OAuth type connections
These connections should be refreshed periodically I believe. If you haven't already would you mind dropping Nintex support an email with this issue, they will probably need a few details, with which we can investigate why the connection is not working.