I got problems to update firmware on old QNAP product.
When I tried to update firmware through web interface I got this error:
[Firmware Upgrade] System update failed. Firmware file format error. Error code: FW004
Solution was:
1. Start reading this interesting article:
How To Update Qnap Firmware
http://qnapsupport.net/qnap-uygulamalari/qnap-firmware-yazilim-guncellemesi-nasil-yapilir/
2. I went on qnap support web page and I downloaded new firmware (and previsious version too)
https://www.qnap.com/i/it/product_x_down/product_down.php?II=107&cat_choose=1
3. On previously link I searched and downloaded and Qnap Finder
https://www.qnap.com/i/it/product_x_down/product_down.php?II=107&cat_choose=4
4. I installed firmware utilizing qnap finder and installation went well.
[update 2019.05.13]
Here they are updated links to all QNAP Storage products:
https://www.qnap.com/it-it/product/