I rely on being able to access my apps to complete many daily tasks and would be equally concerned if I had any trouble accessing them. Rest assured, we are here to help. I would like to gather a few details to best assist. What software version did you update to? Where there any other issues going on with the phone before the update? What happens when you plug the phone into a computer with iTunes (is it recognized)?
Please complete a soft reset: https://www.verizonwireless.com/support/knowledge-base-220219/ Let us know if there is any improvement.