Why has my Android phone stopped updating apps?

My Samsung Galaxy S5 running Lollipop 5.0 has not updated any apps for about 5 days. There are always a few updates daily, so this is not due to a dearth of updates.

I have been to as many helpful sites as I can find in the last 24 hours. I have followed countless suggestions.

I have cleared the cache in the Play Store app. I have uninstalled the updates to the Play Store app. I have done the same thing for some other apps, but I forget exactly which ones. I even uninstalled my account and restarted my phone then reinstalled my account and restarted the phone. Nothing has changed.

After one such uninstall/reinstall, my Google Play Library reinstalled my books, so something is working correctly.

However, when I open the Play Store app and go to My Apps, as with the past 5 or so days, there are no updates to install.

Can you help me?

My next step is to try going in to the AT&T store to see if they can help.

Edit to add: I have now removed the battery, and I’m waiting 5 minutes to put it back in. I will leave a comment as to whether or not this has any effect.