If you are unable to use "Verify Challenge" after completing the exercise, it is possible that there was an issue with the completion of the exercise. Please review the instructions and ensure that all steps were completed correctly. If you are still unable to use "Verify Challenge", you can try refreshing the page or logging out and logging back in to see if that resolves the issue.
@Mohd Qizer Uddin Thanks I've tried above and also the "Verify Challenge" button gives you an update of what's complete and not. In this case nothing happens when you click the "Verify Challenge" button.
I've done the "Reset Pega Instance" and done trying the exercises again (even following the guide video). But nothing seem to validate the exercises.
I have received a response from Pega Academy Support that the auto grading feature of the particular challenge had an issue and that it has been switched off. So that I can mark the challenge as completed manually. Hence marking this question as solved.