Safari 10.1 has modified the way that add-ons can be used. As a result, RoboForm now works from a button/popup toolbar to the left of Address Bar. Upon clicking the new RoboForm extension button, the popup toolbar will drop down.
Upgrade to RoboForm 8 latest version from here: https://www.roboform.com/dist/roboform-mac-v8.dmg to make it work in the new Safari.
The new RoboForm Extension Button:
The Button/Pop up Toolbar: