Cannot be able to use View Tool in Simulation and Device View

I am using Unity MARS for sometimes and recently I am facing this issue. I am not able to use to view tool’s pan and orbit view in. the Simulation and Device View. Whenever I try to use, the Simulation tab gets closed. I tried to use the view tool with both mouse and keypad and but the result is same. I didn’t had this issue earlier so I believe it is nothing to do with settings.

Please help me out here.
Thank You.