Not able to get to other dashboards with beta

Are you sure you have access to their dashboard for the beta version of Nightbot?

As far as I know sub-users/managers from the old version of Nightbot do not transfer over to the beta version, so you would have to be re-added to their dashboard which the broadcaster can do here. Note that they will need your User ID for Nightbot which you can find in the upper right of the settings page.

After you’ve been added as a Manager you can switch dashboards by clicking your user icon located in the upper right-hand corner of the page, and then selecting the desired channel.

Hope this helps!