TimeToSignUp relies on pop-up dialog boxes to confirm certain actions such as deleting items and removing participants from a sign up sheet.
Your web browser might have an option to "Prevent this page from creating additional dialogs." If you enable this feature, you will not be able to confirm actions on TimeToSignUp (and therefore won't be able to perform those actions).
To re-enable dialog boxes, please see these third-party solution articles:
Google Chrome Help Forum - Re-Enable additional dialog boxes
Mozilla Firefox Support - Need to undo "Prevent Site from Creating Anymore Dialogs"
In Chrome, we've found that closing/reopening the tab is the easiest solution. If that doesn't work, close/restart the browser.