It's very likely that you have content control switched on in your network settings, meaning that you won't be able to access certain sites which have an age restriction, such as gambling sites, over mobile data.

Step 1  Go to Settings, then Screen time. Tap 'Content & Privacy Restrictions' and enter your Screen Time passcode. Step 2  Tap 'Content Restrictions', then tap 'Web Content'. Choose Unrestricted Access, Limit Adult Websites, or Allowed Websites Only.