I am adding the service using:

[self.peripheralManager addService:myService];

Is this method deprecated in iOS8.0 or this error might be due to some other reasons?

Most likely some other reason, but we need more code. There is change between ios7 and ios8 in that ios7 permitted operations before the Bluetooth hardware was initialised (power on state) and issued a warning. In ios8 it just fails. Show the code for peripheralManagerDidUpdateState: and how you call addService–  Paulw11 Sep 24 ‘14 at 6:47 

@Paulw has answered this correctly in the comments. Below is the answer

There is change between ios7 and ios8 in that ios7 permitted operations before the Bluetooth hardware was initialised (power on state) and issued a warning. In ios8 it just fails.

So we must wait for the peripheralManagerDidUpdateState: callback before adding any service.

http://stackoverflow.com/questions/26008296/ios-8-0-bluetooth-peripheral-manager-giving-no-callback-for-addservice

iOS 8.0 bluetooth peripheral manager giving no callback for addService