I'm using crnk-client 2.6 to load JSON API resources.
Here is a simplified situation. I have two resources and want to fetch Leads data with Contacts info, however contact field with @JsonApiRelation annotation contains null. Here is this debug session:
How to populate contact field without an additional request?
Seems like something missing on the backend side. Does the leads repository populate contact? If not, JsonApiRelation.lookupBehavior must be setup. And JsonApiRelation annotation be used or a custom relationship repository implemented.
You may also verify the request in a browser to check the server response an exclude the client as source of the problem, but here rather unlikely.