Hello friend, thanks for the update. Please try the following code changes:
First of all give a name to Service Behavior as follow:
<servicemetadata httpgetenabled="true" httpsgetenabled="true" />
<servicedebug includeexceptiondetailinfaults="true" />
<datacontractserializer maxitemsinobjectgraph="2147483647" />
Then associate the Service with the Behavoir name as follows:
By this point the following error should be resolved:
Failed to add a service. Service metadata may not be accessible. Make sure your service is running and exposing metadata.
Try this and let us know your update.