I highly doubt your IP is banned. I've never heard of Itch banning an IP, and secondly, your IP has almost certainly changed more than once since December (ISPs use dynamic IPs, which is the main reason why banning IPs is pointless).
What I have read is that there seem to be problems between the servers Itch uses and some countries. In some cases, it appears to be a blocking issue by the ISPs themselves, and in other cases, it could be that the company managing the servers has blocked certain geographical areas. In either case, it's something beyond Itch's control, so I doubt they can help you.