iPhone apps not working

[patrickstar]

Why wud my iPhone apps appear not to be working? When tapping on apps that I have downloaded, and used the past number of months, now appear not to work and just go back to the home screen? Apps that came with the phone are fine. Thank you

[Gromit]

Have you turned the phone off by holding the top button for a few seconds and and swiping to power off and then turn on again?

or

Have you tried re-syncing your iPhone with iTunes?