Hello,
This product is pretty old, as far as I can see the latest firmware was published in 2012. Did you check if you are installing a compatible firmware version?
https://h10145.www1.hpe.com/downloads/SoftwareReleases.aspx?ProductNumber=JD449A
Please provide the exact name of the firmware file you are trying to copy to the controller! (it should look something like WX3000-CMW520-R3111P12.bin)
Provide a screenshot of the CLI command you are executing in order to start the FTP download! The file should be saved under the name main.bin in the flash of the controller.
Maybe it would be good to use the dir command to check if there is enough space in flash for the new firmware.
Did you test another method of transferring the file? For example TFTP or HTTP?