The PIN is a security code that can protect the SIM card. If the PIN is enabled, it may need to be entered when the SIM card starts in a new device or after a restart.
In a router, an active PIN can sometimes prevent the automatic connection. That is why it is often recommended to disable the PIN on data SIMs that stay in a router permanently.
Do not enter the PIN at random. After several wrong attempts the SIM card can be blocked and ask for a PUK.
Check the SIM card systematically
With problems with a physical SIM card, it helps to separate the card from the router. If possible, test the SIM card in a phone with mobile data and roaming switched on and Wi-Fi switched off. If the internet works there, you know that the SIM card and the service basically work.
Useful links
→ See SIM cards for Sweden and Europe
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