Network issue

Hey there,

Make sure your iPhone is up to date ☞ Update your iPhone, iPad, or iPod touch - Apple Support

also makes sure the airplane mode is not enabled and turn off the VPN if you use it !

also check if there is an update for your carrier settings,Carriers sometimes send cellular updates over the air, independently from an OS update. To check for a carrier update, follow these steps:

1. Open the Settings app.
2. Select General.
3. Tap About. If a carrier or mobile update is available, a prompt will show up on your screen.

If you are still experiencing cellular data issues on your iPhone 13 Pro Max, make sure that the date and time on your phone are set correctly for your time zone. Here’s how:

1. Open the Settings app.
2. Tap on General.
3. Tap on Date & Time.
4. If the date and time are incorrect, update them or turn on the option to set date and time automatically.

If none of the methods above fixed the iPhone 13 Pro Max cellular data not working issue, it may be network related. Resetting the network settings to factory default settings may be the answer to this problem.

How to reset network settings:

1. Open the Settings app.
2. Select General.
3. Tap Transfer or Reset iPhone.
4. Hit Reset.
5. Tap on Reset Network Settings.