Unknown BackendlessFCMService class

Hi.
why BackendlessFCMService class is unknown in the manifest?

Hi,

You may get that error if Backendless SDK is not imported into your application.

Mark

Do I need to create a BackendlessFCMService class or is it in SDK?

That class is in the SDK

I installed the SDK but I get this error again.
I implement libraries to build.gradle file and add below two lines in Application Class:

Backendless.setUrl(Const.BACKENDLESS_SERVER_URL)
Backendless.initApp(context,Const.BACKENDLESS_APPLICATION_ID, Const.BACKENDLESS_API_KEY)

Could you show what you build.gradle file looks like?