@vcapra1 said in Uploads not working:
cluster size 4kb
That seems like an odd cluster size. 32 or 64kb is recommended.
I suggest you take the SD card out of the Duet and use your PC to back up the contents by copying the files. Then use the SD card formatter tool to wipe and format it. It will choose the most appropriate format based on the card.
https://www.sdcard.org/downloads/formatter/
Then copy the files back onto the card and test it out with M39 again and try and upload a file.