My iPhone IP address is banned

Are you referring to your email to someone being rejected or blocked by the receipient's ISP/servers? Or not being able to access certain sites?

That happened to me regularly with a former ISP - two of their servers would be blacklisted because they allowed too much spam /mass mailings to be sent. The only way around it was to reset your router/modem - unplug it for 2 - 3 minutes and plug back in. Most of the time, it would be assigned a different IP address and all was good. My ISP suggested that route and never did accept responsibility.

Banned from what?

Public IP Addresses are controlled by your ISP. You likely have to work with your ISP if there is an IP Address issue.

Snapchat has a way to identify a specific device. So if they ban a user, that person cannot simply create a new account from the same device to get back on the platform.

Users here have found out the hard way they do this by purchasing a used iPhone, only to find they can't login to Snapchat with it because the device has been blocked. In all such cases, it can't be the IP address since theirs would be different from the person who sold the phone.

In short, it's not your IP address that's been banned (despite the message), but your device.

If that were true, you wouldn't be able to access anything on the Internet, including here.