Symptoms
When loading the K2 form, the forms remains in the loading status. An icon is shown that indicates that the form is loading. When hitting the F12 button, there is an error message that states that a _debug variable is not defined.
Diagnoses
From researching the error, it appeared to be caused by a Set Language Custom Control that is not implemented correctly. Requested client to verify if the Control is deployed and being used correctly.
Resolution
Client identified a typing mistake in the translations used by the Control that caused the pages to fail to load. Rectifying the mistake resolved the error.