Symptoms

Worklist control hangs on spinner when there are items on the worklist. Performing a debug shows this error..
Unable to get property 'split' of undefined or null reference
Failing on this line of code...
var aq=JSON.parse(this.FilterObject),rq=this.options.hostURL,gt=rq.split("/"),uq=gtt0]+"//"+gtt2]+"/K2Services/rest.svc/Worklist/Items",w=this
There is no hostURL on the options object..
 

Diagnoses

Looking a little deeper... This is the DIV for the Worklist control... Notice that the hostURL under options is null or empty
data-options='{"serverControlType":"SOURCECODE FORMS CONTROLS WEB CONTROLPACK WORKLIST WORKLIST WORKLIST","text":"Worklist","activityName":"Grid","RefreshInterval":"300","Rows":"20","ActionMenuItemData":"release,sleep,redirect,share,viewWorkflow","WatermarkText":"No tasks to display","fileVersion":"4.15050.16054.1","hostURL":null,"columnLayoutConfigurationValueHolder":":{"key":"ActivityName","value":"Activity Name","width":""},{"key":"Folio","value":"Folio","width":""},{"key":"EventStartDate","value":"Task Start Date","width":""},{"key":"ProcessName","value":"Workflow Name","width":""}]"}' unselectable="on" data-widget="worklist" name="Worklist"andgt
 

Resolution

Check the "Web Service URL" and "Web Service URL SSL" environmental variable, make sure they are correct and not empty.
Check the environmental variable from workspace andgt management console andgt Environment Library andgt Templates andgt Environments andgt ...