I dug a little more and found because of the way Codepen is implemented with iframes, you must use the following to refresh the page.
window.location.href = window.location.href;
Actually, your pomodoro clock should have a way to reset before it gets to the “end” in case you want to change your clock settings. Also, you should not be refreshing the page to start over. Instead, use JavaScript to create an initial “state” for your application. This initial state could include specific default values for session and break times and all timers would be cleared. Refreshing the page is a band-aid and does not harness the dynamic power of JavaScript DOM manipulation. Refreshing the page takes much more time and the user has to wait while it loads. Doing everything with the existing page is much faster and slow internet connections do not affect your applications functionality.