The APN appears only when you insert the SIM or you download the e-SIM, it tells the phone how to access the internet or send MMS.
You have to upgrade the operating system iodéOS to the next version 7.x, if you hit the Updater icon or search in Settings > About phone you should be still at version 6.9 or somehting like that.
For the time being they are doing some maintenance and you won’t find the update files so you have to wait but read this to be prepared, Trying to update from 6.3 to 7.0 (but no WIFI, and no mobile data) - #4 by george