Hello,
From your screenshot, it seems you use both internal and external flash, I don't think the IDE can download both flash at the same time. How about create a project only use external flash, and use flash driver "LPC40xx_SPIFI_GENERIC.cfx" do download, also delete the internal flash:
Alice_Yang_0-1658914425560.png
There is demo under LPCopen, while they all use internal flash, you can change base on them.
BR
Alice