Hi
I had a similar pb, my picomax was downloading, checking and then told me that this was not a valid update package.
I was stucked on 1.1.03…
I did an OFFline update to 1.1.04 by downloading the firmware to the root of a microSD card (FAT formated)
Don’t forget to rename the file to update.zip
Then went back to update->offline…
Once done (updated to 1.1.04) i could check for update and update to 1.2.1 ONline as normal.