Dashboards that used to have export buttons in dashboards now have dissapeared.
No Error
The exportable settings is probably not enabled.
Go into the configuration for the dashboard widget by going to:
Admin > Dashboards > Find the dashboard > Click Edit at the top
1. Click the edit button (looks like a gear) at the top right
2. You will notice under the widget's title a "Can Export:" section
3. Make sure this box is checked.
4. Save the widget.