G-Code viewer doesn't work

Hello. I need help with G-code viewer.
Octoprint runs on raspberry pi 3 b+.
I use Simplify3D to create G-code. My printer is Rf2000 v2.
Most things work except to cancel printing and g-code viewer.
The G-code viewer doesn't work at all.
It does not matter if the file is on the sd-card or i download it to raspberry pi.
It doesn't matter whether the printer is printing or is idle.
It doesn't matter the file size.
The viewer does not display a small file as well as a large file.
The installed version of Octoprint is 0.16.0.
Do I need to install a plugin? Did you forget to turn on something,
somewhere in some settings?

Try clicking the box to center the image. It may just be outside of the view port.