Problem: It does not save the APN configuration or does not connect to the APN
At first let's try the following steps if we can't save the APN.
1. Activate only the GSM option and exit to save
2. Activate the 3 parameters below and exit to save
3. Check that you have coverage once the card is inserted.
4. Access the SIM and set the APN settings (APN, user and password)
Here is a list of operators with their APNs, users and passwords. Vodafone and Movistar almost never need username and password. http://www.apn.com.es/
You should also take into account these frequent errors:
- SIM without balance
- SIM without 2G (for the HUB)
- APN for MMS and not for data (we need the data APN)
* Sometimes it is possible that it does not allow you to modify the APN even though it recognizes the card (known case with DIGI MOBIL), in this case change the SIM card for another company and modify the APN we need and put back the SIM card.