General reasons for a list to be empty. Reasons are either related to a summary list (i.e. problem or medication list) or to a workflow related list (i.e. consultation list).
API
Project FHIR API
This is the location where you can find your resource using a FHIR client.
Simplifier FHIR API
The global endpoint is where users can search for all resources in Simplifier. Resources have a globally unique guid Id here.
