This article explains how to unlock the OSD buttons on my Elo products

This process can differ between units, so please refer to your user manual for your specific product. 
Example of process:

• Press and hold the “Menu” and “Up” buttons for two seconds to enable/disable the OSD Locking feature.
• When the OSD Locking is enabled, pressing any of the Menu, Up, Down, or Select keys will have no effect on the system.