This got solved when I used another image located in Firmware\buildroot\Luckfox_Pico_Mini_Flash\mini_buildroot_spi.
Could you tell me the use of the backup folder and why the image kept there did not work?

Hi, I have a Luckfox Pico Mini B and I went through the tutorial of Flashing the SPI NAND Flash. I flashed the image from Firmware\backup\luckfox_pico_mini_b_image available on google. I have disabled my Public and Private network firewall and setup the static IP of this Pico device to 172.32.0.100 ...