This usually means the Smart Card is loose. Open the Box (if out of warranty) and re-seat the SIM card inside, or try cleaning the contacts with an eraser.

You will need an active connection for the initial "Sync Settings" and server-side activation.

The latest versions of UFI Box (v1.7.0 and above) have significantly improved and Oppo/Realme Auth-free flashing capabilities. By following the GSM Forum setup standards, you ensure that your hardware is protected and your software is optimized for the latest security patches.