It's alright, it will eventually work. I had this same problem at the start of last week for about 4 days. I couldn't receive any code from Instagram at all and I have 400 Insta accounts!
They've been updating their phone verification system from the looks of it. I've seen a different looking verification screen pop up on some accounts and it seems to be behaving differently - not accepting a few of my phone numbers when setting up new accounts, keep on getting repeated PV's for some accounts etc...
It may have just been coincidence when it started working again but I tried verifying a few of my accounts with a few new SIM cards. Once the SIM card was activated (usually have to wait about 10 mins and turn airplane mode on/off a few times), I entered that number into Instagram and voila, I finally received a code from them and then all my old stored SIMs started working again with Instagram.
So, generally speaking once you get one SIM and account to verify, the rest should work again. If your setup isn't big and you're still struggling to gets codes, try buying a few cheap aged accounts and getting them to the phone verify screen and see if you can receive the codes from those accounts.