Obvious to some but when you click on share to Facebook you are confronted with a share popup that asks you to use your personal Facebook account. In this particular case you want to share directly to your business page but it was created using your login for your personal account.
I finally came across the fix for this today and happy I did.
On the popup window, simply click on the share on your own timeline and instead select “share on a page you manage”. Viola.