I have my LightROM on; i always keep a backup of my latest working ROMs before i do anything, saves me a tooon of headacheDo you have a backup of this device when it was still working that you can restore? Otherwise doing an EFS backup now with your phone not being able to connect to the cellphone network doesn't seem to make any sense to me.
Honestly I never had to deal with restoring EFS partitions. I did a backup of this partition before flashing LOS 19 the first time. Because I messed up at a later point I repeated a clean install but without EFS backup, which also worked fine for me.
Another silly idea: Did you check the tray which contains your SIM and sd card? Maybe it is not sitting the supposed way (although the tight space doesn't seem to allow for this).
And ye, i did check the sim and card; because after i checked it and went to my old ROM it was all working fine.
I *do* think the actual sim card worked at the start? I think it connected to my mobile internet and everything but then when i was installing apps and checking for bugs i noticed the sim card was lost
And what I was asking if i can put the previous custom ROM's EFS with the new (LOS) one, because I have some stuff like my bank app that uses the IMEI address or something of the device so it saves me several days of headache trying to register it by going to the bank.