Mobile Data troubleshooting

Some local mobile operators may not work out of the box. Here are some steps to take to fix this:

Enable data roaming
Example: NRJ Mobile in France
Despite NRJ mobile being a french operator, it relies on the Orange network, so the data roaming needs to be enabled.

Settings -> More -> Mobile Network -> Data roaming

After doing so, select the "real" operators:

Settings -> Sim management -> Roaming -> Data roaming -> Select Orange

Then verify that the correct APN is selected:

Settings -> Mobile Networks -> Access Point Names -> Select an existing one or create on if needed

Finally check that mobile data is enabled

Settings -> Data usage -> Mobile data