Grid Repeating Layouts are set to Read-Only by default.  You can make them editable by opening the Layout Properties and change the settings in the "Row Operations" section of the "Operations" tab:

Sincerely,

Henry

Self-Study Support

Pega Academy

Whenever you launch an Assignment and you have permission to perform that Assignment you will be presented with the Harness configured on the Assignment, either Perform or some screen flow Harness.

If you click on My Cases you are opening Work - a case may have multiple active Assignments - which would it launch?

Hence when you do "open Work Item" you see a read-only Review screen that, in turn, shows you what Assignments can subsequently be opened.  

See doUIAction.

In Repeating grid, column pyID property is link control, go to action tab for this control and add event click action should be Open Selected Item will open work object in review harness.