By default, the Duplicate Status Visual Force Page is set to a height of 25 pixels. Unfortunately, on small screened devices, this can result in the Find Duplicates and Assign Duplicates buttons stacking on top of each other, and the Assign Duplicates button being hidden from view.
If the Assign Duplicates button appears to be missing from the layout when viewing a contact record:
- Go to a contact record and in the upper right find and click on Edit Layout
- In the Edit Layout screen find the Duplicate Status Visual Force Page and hover over that Visual Force page
- Click the wrench icon to edit the properties for the Duplicate Status Visual Force Page
- Adjust the height in pixels to a number great enough that it will allow the buttons to display when stacked on top of each other
- Click Ok
- Click Save