Judging from the URL you posted, I’m guessing you’re using a THETA S. I just tested updating the firmware on my THETA S. I ran into one or two things that hopefully might help.
I was at firmware version 1.10.
I had to charge my THETA more before I could do the upgrade.
What I noticed was these directions. When you click OK to update the firmware, you’re downloading the latest version of the firmware, in this case 1.90, but not installing it yet. Here’s the sequence:
When I disconnected it from the USB cable, the camera turned off. When I restarted it, the camera and video icons on the front were flashing blue. That lasted only about 20-30 seconds.
I connected the USB cable, and checked the firmware status. Updated successfully.
Hope this helps.