You need to set the Serial Number because it is blank by default.

• Under the Guest (NIOS-X host), go to Options > SMBIOS Settings (Type 1).
• You will need to fill the Serial number value in. You could use the MAC address of the first network adapter. To get that, Exit and got to Hardware (two items above Options). Double click on the (net0) and copy that MAC addrsss. Go back tinto SMBIOS and past it into the Serial field.
• Reboot.

Automation snipit

VM_ID=999  # Replace with your actual VM ID
SERIAL_NUMBER="abcd1234" # Replace with your serial number
# Set the SMBIOS base64 encoded serial number and UUID for the VM
ENCODED_SERIAL=$(echo -n "$SERIAL_NUMBER" | base64)
echo "Base64-encoded serial: $ENCODED_SERIAL"
# replace SERIAL_NUMBER with its base64 form so the later qm set uses the encoded value
echo "Setting SMBIOS serial number to $SERIAL_NUMBER and UUID to $CURRENT_UUID..."
qm set "$VM_ID" --smbios1 "$CURRENT_UUID",serial="$ENCODED_SERIAL",base64=1

Alternatively, use seed.iso/metadata.iso cloud-init cdrom file ( which don't need serial Number which is needed for device login) via this you can configure both jointoken and proper network too. So refer the docs here and here