Symptoms

Worklist control empty, won't load data (infinite spinner).
 

Diagnoses

Browser console revealed an error

"Uncaught TypeError: Cannot read property 'split' of null"

regarding a line in the Web Control Pack JavaScript bundle

'populateArray:function(t){this.GlobalArrayOfWorklistItems=s]var aq=JSON.parse(this.FilterObject),rq=this.options.hostURL,gt=rq.split("/"),uq=gtg0]+"//"+gtg2]+"/K2Services/rest.svc/Worklist/Items"'

which likely crafts a call to the REST service using the Web Service URL "this.options.hostURL" which was null at runtime.

 

Resolution

The intended Web Service URL environment field was not set as the default.