Depending on your personal phone model and settings, the touch box for the Stop Alarm button can be slightly off. Navigate to the settings tab represented by the gear icon and locate the Alarm Stop header. Switch over from “Hold for Off” to “Simple Off” option so that you can stop the alarm by just pressing the home button.
If this does not solve the problem, restart your phone and contact tech support from the in application settings page.
Android users should contact tech support immediately after restarting their device. Tech support can be accessed from the profile page represented by the person icon at the upper right hand corner.