Marlin does not send "File opened" message to host (Octoprint)

I'm not sure if this is a problem with Octoprint or Marlin 2.x, but as the problem didn't occur with the original firmware of my Sapphire Pro, I suppose asking here is a reasonable start.

The problem is that the printer never signalizes to the host when I start printing from SD card on the touch display of the printer. Instead it stays in "Operational" mode.

It does receive other messages, e.g. temperatures and "SD printing byte" messages, just not the "File opened" message. When looking at the serial.log, there is no "File opened" message (or errors) either. Just the standard response and temperature/progress messages from the printer.

I've tried to insert a M118 gcode into every gcode file to send a "File opened" message manually. But while it does receive that message and change the state from "Operational" to something else, the print progress doesn't work properly (shows over 100% after a short time), and timelapses don't work at all.

Everything works properly when starting a print through Octoprint, but I prefer starting prints on the display of the printer.

Does anyone have a similar problem with Marlin and Octoprint? It still occurs with Marlin 2.0.4.4.

The problem has been solved. It was a configuration problem. And there'll probably be a patch for Marlin which prevents this problem from happening again in the future.

The Configuration.h I used included these 2 values:

#define SERIAL_PORT 3
#define SERIAL_PORT_2 1

Since I changed them into

#define SERIAL_PORT 1
#define SERIAL_PORT_2 3

everything works as it's supposed to.

I stumbled across this post. I waited for so long for someone to have the same issue.
I will try this solution! Hope it works!
I only have one question... Do we know the code background for this and why doing this solves it?
I'm not skilled for this, only trying to understand.
Thank you!!!

Some messages are only sent to SERIAL_PORT

SERIAL_PORT should be the main controller, in some cases this is the raspbury pi, but for touch screens they are really a controller so that should be on SERIAL_PORT

Thank you! I'm updating marlin right now with this setting to see if it works.