Since a new APN system for AOSP ~early 2026 some ideas for troubleshooting include special attention to actively harmonising the APN data:
- on your SIM card,
- provided on /e/OS install and
- your carrier’s latest APN.
APN will likely fail if the SIM card data (for any reason) cannot be updated to exact current values. Understood; many of the following you did.
In case of difficulties one can ask the carrier to do an APN reset OTA (Over The Air) … alternatively
Manual APN Configuration
Ensure you have a good Wi-Fi connection.
Open Settings 
Search APN … or
Navigate to Mobile Networks:
Tap on Wireless & networks or Connections.
Select Mobile networks or Mobile data.
Access APN Settings:
Tap on Access Point Names or APN.
Add New APN:
Tap on the ‘+’ icon or Add button to create a new APN.
Enter APN Details:
Fill in the required fields based on your carrier’s specifications.
Save APN Settings:
Tap on Save or the checkmark icon to save the new APN.
It is OK if Save takes a while complete … implies the the settings have been checked valid by the carrier. Note: Add new APN seems more likely to succeed than Edit existing.
Troubleshooting
If you encounter issues while setting APN, consider the following steps:
Reset to Default: Navigate to APN settings, tap on top right 3 dot menu, and select Reset to default.
Activate Airplane Mode: Enable Airplane mode, wait for a few seconds, and then disable it to refresh the network settings.
Remove SIM Card: Remove the SIM card, navigate to APN settings, make changes, reinsert the SIM, and restart the device.
Restart Device: Restart your phone while connected to Wi-Fi to refresh the network settings.
Carrier-Specific APN Settings
For specific APN settings, refer to your carrier’s documentation.
IMS Registration
In order for all data and call features to work you need to know that your IMS status is registered. A guide to dial INFO.