What is the problem?
No image at gcode viewer tab when I click on a gcode or upload one.
What did you already try to solve it?
Search this forum, google and plugin page to see that maybe I need to enable something or install a plugin. Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)
MK3 with pi zero installed on its native port.
[Goodeid]'s suggestion worked, for the local loaded files, not SD. Maybe the viewer is not able to show the SD one anyways. I still had to do reload to see it and just loading did not work. Thanks!
[jneilliii]'s suggestion did not work for me, on local or SD. Still thanks!