Sometimes the permissions with your iPhone get reset. 1 Second Everyday needs these in order to work properly. To make sure the app has the correct permissions please go to 1SE "Settings" and tap on "Manage Permissions".
This will take you to your phone's settings option for 1SE. Make sure everything is allowed and 1SE should be working fine.
TIP: Everything toggled on already but still doesn't work? Try turning these off, and then, back on. Sometimes the reset helps.