Uncaught SoapFault exception: [soap:Server] [AuthenticationError.CLIENT_CUSTOMER_ID_INVALID @ ; trigger:'<null>']

[Bappa Sk]

Hi Vincent, 

I am getting error:

Fatal error: Uncaught SoapFault exception: [soap:Server] [AuthenticationError.CLIENT_CUSTOMER_ID_INVALID @ ; trigger:'<null>'] in /home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/Google/Api/Ads/Common/Lib/AdsSoapClient.php:221 Stack trace: #0 /home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/Google/Api/Ads/Common/Lib/AdsSoapClient.php(221): SoapClient->__soapCall('get', Array, NULL, Array, Array) #1 /home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/Google/Api/Ads/AdWords/Lib/AdWordsSoapClient.php(86): AdsSoapClient->__soapCall('get', Array) #2 /home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/Google/Api/Ads/AdWords/v201603/ManagedCustomerService.php(4485): AdWordsSoapClient->__soapCall('get', Array) #3 /home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/test.php(34): ManagedCustomerService->get(Object(Selector)) #4 {main} thrown in/home/tistasoft/public_html/linkbuildingcompany.biz/googleads/google-api/src/Google/Api/Ads/Common/Lib/AdsSoapClient.php on line 221

How can I resolve this issue? Please help me.