So it’s complaining about this line:
GlobalVariable.cookie = CustomKeywords.'aem_api.Aem_Author_Api.LoginToAemUsingApiAndFetchLoginCookie'(userName, password, authorUrl, loginResource)
Yet the error message is complaining about a resource identifier that differs from this:
cms_api._Author_Api cannot be cast to groovy.lang.GroovyObject
So there’s a discrepancy between what the compiler thinks you are trying to do vs. what your current script shows:
cms_api._Author_Api
vs.
aem_api.Aem_Author_Api
Have you recently renamed any packages/classes in your Custom Keywords? The best quick fix I can recommend is this:
… which basically recompiles all of your project code.