Can't enter calibration mode
I have Nybble cat with board V1_2.
I managed to configure Arduino and run buzzer test successfully.
Then I followed the instructions in several documents saying that for calibration I need to upload WriteInstinct.ino, but it doesn't exist in the latest repo, so I assumed it was combined with OpenCat.ino and all the calibration logic should be there now.
I then opened OpenCat.ino, uncommented the line with my board version, commented out the default one, and commented out MAIN_SKETCH line.

I turned on the power, opened the monitor and uploaded OpenCat.ino.
It asked me if I wanted to reset joints offset, I said Yes.

It asked me if I wanted to calibrate IMU, I said Yes.

And now I assumed I should type 'c' to enter calibration mode, but nothing happens.
What do I do wrong? Have I missed anything? Please help.
Found where I took that doc link from - https://www.petoi.camp/forum/basic-assembly-and-setup/assembling-instructions