Cannot load project to controller due to unknown error

[Kevin L]

I am trying to replace a PDF file with an edited update of the same document but, no matter what I try, a message window appears with "cannot load project to controller due to unknown error"

I have even tried a PDF file totally blank, other than the word "test", no joy

Strangely, I can replace the file with another that has already been downloaded

I'm mystified!

[Saragani]

Are you downloading it to the external SD?

Is there a chance that the external SD has been locked? (There is a system tag regarding the SD, with a member called "Locked" or "Is Locked")

Rebooting the PLC if that happens can sometimes help.

[Kevin L]

Overcame the problem by removing the SD card and downloading the files directly to it on my laptop