Because your original QCN file is likely corrupt, you will need to download a clean "POCO X3 NFC surya clean QCN file" from a trusted development forum (like XDA Developers).
Flashing incompatible firmware can wipe the EFS partition, resulting in an "Invalid IMEI" message. repair imei poco x3 nfc
Open the dialer and type: *#06#
Go back to > Developer Options and enable USB Debugging . Connect your phone to the PC. Because your original QCN file is likely corrupt,
Your original, valid IMEI numbers should now display correctly on the screen. repair imei poco x3 nfc