This happen when the validation certificates fail to renew. you could try to do a factory reset, this normally fixes the issue, but can also return depending on the device. Also make sure your provider, will be willing to put everything back onto the device if the factory reset removes all your previous stuff. You can check to see if you can download a backup application for your device, yes i know, normally you would find this on google play store and thats what is not working. What you could do is use another device and save it onto a USB drive, then install it from there. Once you have done everything and got it working again try and find a new google play install and get an updated version, yes this is not easy, but if you look hard enough you should be able to find one… that’s your only option… or buy a new device.