How to resolve app connectivity with internet issues on iPhone?

Perhaps a long shot:

Do you have a 3rd party VPN installed, even if you are not using it? If so, delete the VPN profile in Settings/General/VPN & Device Management/VPN, then restart your device. Don't just turn it off; delete the profile. If that fixes it, you can try reinstalling VPN, but probably shouldn't.

You can force-restart:

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY for the first two buttons, then a long hold for the SIDE button; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem. 

You should also try restarting your router, and if that doesn't help, a network reset:

• Open Settings
  • Tap General
  • Tap Transfer or Reset Phone
  • Tap  Reset
  • Tap Reset Network Settings

• • This will erase all Wi-Fi passwords, but will not result in any other data loss.

SravanKrA wrote:

Have you tried Settings > Cellular/Mobile Data > [Scroll Down]? See here which Apps (Specific apps like McDonald’s, Sonic, and Little Caesars) are disabled. Enable them selectively.

Great suggestions!

Have you tried Settings > Cellular/Mobile Data > [Scroll Down]? See here which Apps (Specific apps like McDonald’s, Sonic, and Little Caesars) are disabled. Enable them selectively.