I have a one plus 3T Oxygen 4.1.7.
I can no longer download/update apps on the Playstore without wifi, I used to be able to until I accidentally checked to always download over wifi only.
Here are the things I tried to fix it.
I've already changed : Play Store > Settings > Auto-update apps to Auto-update apps at any time. Data charges may apply.
I've also changed Settings > Google > Data Management > Update Drive-enabled app files - Over wifi or cellular.
I've uninstalled play store then reinstall as well as . I've restarted multiple times after each of the above steps. So far nothing works.