Unfortunately, it's not an issue I can replicate on my end and I'm testing this using the same v0.1.0 build that is available in everyone's accounts. The EFB can be powered off by pressing and holding the home button as seen in the following screenshot:
EFB Power Off.jpg
The only things I can think of that may be causing that issue is:
An activation issue: Can you confirm if you have any error message on the EFB such as "License Failure" or "Loading Aircraft"?
A controller assignment issue: I would suggest going to MSFS Options > Control Options, selecting your mouse and then selecting the "Default" preset. This will ensure your mouse is working as expected and that it doesn't have a control assignment issue.
An addon conflict issue: This could be caused by a conflict with the RJ and another addon in your Community folder. We aren't aware of any conflicts at this time, so the easiest way to test this will be to rename your Community folder to something like "Community.old", then create a new Community folder named "Community" in its place, and install the RJ into the new Community folder. Then launch the sim and test the EFB power functionality. If the power functionality works, then we can deduce that there must be a conflict with another addon in the community folder.
Mark - Just Flight