Since you're using the Reddit app, it's not just your IP that's banned—it's your device ID and Android/iOS advertising ID. The app reads device hardware specs directly, so making new accounts on the same phone will get them instantly nuked.
To bypass this, reinstall the app, clear all app data, reset your device advertising ID (GAID/IDFA), and use a fresh residential or mobile proxy. If that still fails, switch to an anti-detect browser on a PC instead of using the mobile app.