If the Share button is not displaying at the bottom left of your Collection dashboard, your Collection is likely still in Preview mode, or the collection is set to Hidden status. In order for the Share button to display, your Collection must be published and set to Show status.
Only "Preview" and "Publish" Buttons are Displayed
This simply means your Collection has not yet been Published! Simply click the Publish button on the bottom left of your Collection dashboard to publish the Collection. Once the Collection has been published, you will see the Share button displayed.
Only "View" Button is Displayed
If you are only seeing the View button, your Collection is likely in Hidden status. When your Collection is set to Hidden, this means it is no longer published and is not visible to your clients.
1) To publish, simply click the green Quick Edit icon (pencil) next to your Collection title.
2) Change the status to Published in the drop down Status bar.
If your Collection is Published, but you're simply not seeing the buttons in your Dashboard at all, it's likely that you are viewing the browser in a zoomed in/magnified view which has caused the buttons to become hidden. This is a super easy fix though - just adjust the browser zoom/magnification level and the buttons will reappear!
On a Windows/PC Computer: use the CTRL - buttons on your keyboard to manually decrease the zoom level
On a Mac Computer: use the Command/CMND - buttons on your keyboard to manually decrease the zoom level