Installing and switching on are separate steps. A profile that is installed but left off makes no attempt to attach. Open the SIM menu, confirm the right profile is enabled, set it as the data line, turn on data roaming as your plan instructs, then cycle airplane mode once.

It genuinely helps, and for a real reason. Airplane mode shuts the radios down and drops the state they were holding; switching it off restarts the scan from the beginning. A large share of these problems come from a phone still holding the previous country's or tower's state, which is exactly what the reset clears.

Treat it as a later option rather than the first. Try airplane mode and a restart first; if those fail, turn automatic selection off and work through the list one network at a time. Switch back to automatic afterwards, or the phone may refuse to move to a better network as you travel on.

Registration has succeeded; the trouble is in the data layer, which is separate. Check that the data line is the travel plan's line, that roaming is enabled on it, and that the APN matches what the plan specifies. A value left over from hand-editing on an earlier trip is a common culprit.

There is no fixed figure; it depends on where you are, how many phones are attaching at the same moment, and the network itself. It normally settles shortly after airplane mode goes off. If several minutes pass with no change on screen, start working through the troubleshooting order rather than waiting longer.

Most traveller plans need it on, because you are using a network that is not the profile's home one. The toggle is only permission inside the phone, not a pricing decision; charges follow the terms of the plan you bought. If your home line is still active, turn its data off separately.