Reset Your Network Settings
Another possible fix you can try is resetting your network settings and see if that does the trick.
- Open the Settings app.
- Go to General.
- Scroll down and tap on Transfer or Reset iPhone.
- Tap Reset.
- Tap on Reset Network Settings.
- Confirm that you want to reset your network settings. You may need to enter your passcode to continue.
Your iPhone will restart itself and reset all your network settings. Keep in mind that this will not delete any content on your iPhone. But it will reset Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used previously.