Alice_Yang
Thanks for your suggestion. I already tried Flash Magic before which constantly gives below error.

So I moved to use LPCScrypt.
converse
But using LPCScrypt I am able to successfully program the LPC54628.
Now I have further updated is like bootloader which I programmed using LPCscrypt is running fine as I verified it by prints coming on the serial port. Now a new problem is started that every time that bootloader ran even I programmed new or erase that.
So not sure what is the issue? is it possible bootloader written somewhere else in memory and locked once it programmed?