If your your Business Page isn’t showing available to link to your Group, then you may have to switch your Business Page back to Classic. When Facebook created the “New Page Experience,” it’s seen some glitches and recommends the switch for now in order to post to a Group and manage a Group as your Business Page entity.
To switch back to classic Pages on desktop (not available on mobile):
Open your new Page.
In the menu beside Edit Page, click … and select Switch to Classic Pages. If you do not have the option showing “Switch to Classic Pages”, then you will need to create a new Business Page.
Follow the flow, and select Continue.
This will switch your new Page to a classic Page.
Then, go back into CinchShare and visit your Networks page. Click Refresh.