Unable to read file install_linux_fw_sd.scr

Following directions at https://www.digi.com/resources/documentation/digidocs/90001514/task/yocto/t_program_firmware_yocto.htm?tocpath=Digi%20Embedded%20Yocto|Get%20started|_____3.

Using Ubuntu 64-bit 18.04.01 on VMWare image.

MicroSD card formatted to FAT32 on Windows 10 device. Using GtkTerm. Successfully set serial port parameters and rebooted. Last message before terminal prompt at GtkTerm is ‘Hit any key to stop autoboot: 0’.

At terminal prompt of GtkTerm, run install_linux_fw_sd gives error: “Unable to read file install_linux_fw_sd.scr”.

Sorry if this has been asked before. Grateful for any assistance or advice.

are you doing this on uboot prompt?
Can you please paste a console log?