In order to stream to a Facebook group or page, you must be an admin for that group / page. You can follow these steps to confirm that you are an admin.
Note that page editors and group moderators are NOT admins (even though they have many similar privileges).
Confirm I'm a Facebook Group admin (Desktop)
If you are on mobile, the no easiest way to confirm that you are a Facebook admin looking at a recent post.
If unable to confirm on mobile follow these directions on a desktop computer.
When using Facebook on a desktop computer, navigate to your group. Click on MORE >> MEMBERS.
You will see your Admins and Moderators listed together. Make sure that there is an ADMIN tag below your name.
Confirm I'm a Facebook Page admin
Navigate to your page. Click on the gear (on a desktop browser, find page settings).
Click on Page Roles.
Confirm that you are an admin.