SPARQL Query tab in Protege doesn't show anything

It happens in version 2.0.1 of Protégé SPARQL Plugin, bundled with Protege 5.2, after any ontology is loaded.

 

Update the the "OWLAPI RDF Library" and "Protege SPARQL Plugin" to the latest version with the auto-update mechanism (which appears when starting up Protege or can be activated through the File > Check for plugins… menu):

 

Source: https://github.com/protegeproject/sparql-query-plugin/issues/10.