Your customer has landed with no internet: the 5 checks
To read with them on the phone, in order. After each step, ask them to open a website to test.
First of all
They must never delete the eSIM: it cannot always be reinstalled. They must not turn off their usual line for good either: they would stop receiving calls and SMS.
The 5 checks
The eSIM only connects once there.
In Orders: the right country, still valid, data remaining.
iPhone: Settings › Mobile Data › Mobile Data. Samsung: Settings › Connections › SIM manager › Mobile data.
iPhone: Settings › Mobile Data › Sirocco line › Data Roaming. Samsung: Settings › Connections › Mobile networks › Data roaming. On this line only: their usual line is not charged.
For the test only. Then turn their usual line back on.
If that is not enough
The full path is in the Help guide of your space, in the "It isn't working" section: switch to 3G, choose the network manually, remove the physical SIM card. If your customer cannot manage, the assistant answers 7 days a week, and you can talk to an adviser from your space.
Countries with special rules
The phone has a signal but nothing loads: change the network name, called APN. The name to enter is in the Help guide.
Operators cut data for 24 hours on the first connection. It lifts on its own. Tell your customer before departure.
The eSIM cannot be bought or installed from the UAE: install it before departure.
€10 free for a real eSIM. Free sign-up, no subscription.