When I flash my new custom rom, I still didn't notice that I can't use my mobile data. When I get RR as my permanent rom, when I checked the mobile data, it's not working anymore. I tried flashing every rom, but it's not really working. I tried all solutions, APN, factory reset, efs everything! But it's not working. I reverted back to the stock rom, and it's working. Flash a new rom and it will no longer work. What do you think is the problem?