Hi Erick,
It looks like you’re on the right track — the behavior you’re seeing is expected when the storage backend isn’t properly initialized. The 550 Can’t open directory / error usually means the filesystem (in this case SD) isn’t mounted or recognized correctly by the FTP server.
When switching from STORAGE_LITTLEFS to STORAGE_SD, make sure a few things are properly set up:
The SD library is included and initialized before starting the FTP server
SD.begin(SD_CS_PIN) is called successfully in your setup
The correct SPI pins are configured for the Pico W2 (since defaults may differ)
Also double-check that your library version actually supports STORAGE_SD for RP2040 — some builds only partially support it, which can cause compilation errors
If you’re still getting compile errors, it’s often due to missing defines or incompatible storage drivers rather than your config alone.
If you can share the exact compile error, it’ll be easier to pinpoint what’s missing
