GL-X3000 firmware installation fails and router no longer boots

I tried a firmware update on the web interface when prompted to do so. It couldn't be done and the router didn't restart. After that it wouldn't boot anymore (only the power LED lights up). Then I tried it via uboot. It didn't reboot either. I also tried a different power supply (12V 5A). That didn't change anything. I can still access the uboot web interface. What else can I try?

Please contact my colleagues support team: support@gl-inet.com. Thank you.