Could Not Launch Appium Inspector


I am new to iOS automation using Appium. Initially I was able to launch the test app through the appium inspector from the GUI without any issues. All of a sudden I am getting the following error message

Could Not Launch Appium Inspector
Could not get list of sessions from Appium Server
Be sure the Appium server is running with an application opened by using the “App Path” parameter in (along with package and activity for Android) or by connecting with selenium client and supplying this in the desired capabilities object.

Appium: v1.5.3
Xcode: 7.3.1

I double checked, the server is running in the background and the App Path has the valid path to .app file. Could someone help on this.

Thanks in advance.