A few things to check prior to using the share link feature:

• Save the diagram by clicking on the save icon found on the top-right corner of the toolbar.
• Go back into the project menu where your diagram resides and activate the shared toggle button.
• Head back into the diagram you wish to share and click on the share link icon.
• The link that can be used to share the diagram should be presented.

Have a look at our Share a diagram how-to guide for other ways to share your diagram. 

If you are still having trouble, please get in touch via email to support@bowtiemaster.com