Generally in UserAlgorithm.c, you will find:
static uint8_t algoType = AHRS;
it means heading calculation from mag, pls check.
Already enabled in VG_AHRS app on ANS( developers.aceinna.com/code/apps), you can test.
Just a reminder, we didn't calibrated the 300ZI mag in plant, for mag is too easy influenced by environment. and you need to calibrated by your self if you need, steps in topic_11(https://forum.aceinna.com/topic/93/top-topics-of-common-operations-with-openimu-products/2)

Pls refer to SW protocal of UART/SPI:
https://openimu.readthedocs.io/en/latest/software.html#openimu-software-support
HW interface as:
https://openimu.readthedocs.io/en/latest/OpenIMU_Modules.html#openimu-modules

@rintaro if it worked and will give feedback, if not you need change the baud rate and try again:

SW/Algorithm Reset generally no problem, cannot lead output data 0.

I still want to know what other actions you had done? e.g. send some commands to IMU.
for the CAL/CONF area may be already broken, but generally you cannot break it only by boot loader(boot loaderworking fine now) except some special commands received. or it can be recover well.
so i need time to find solution to recover your CAL/CONF area, working on it.
if you have other more information, pls let me know.

@rintaro you need to do:

• send commands to 300RI to lock one sector of the Unit, by UART.
  

• power off and on, running with python diver and connected by ANS web page. maybe you need to change the packet rate, and click play button. check whether some data output.
  

• after connected by ANS web, pls upgrade to below app, then power off an on, check how the status is in your side.
  

still find solution, still need more time, I can't reproduce your phenomenon now.

@akofler I had finished the 300RI...109 bin file preparation and shared with you, pls follow the topic_4 steps, note that just starting from unlock step and then upload/lock steps followed.

109_with_VG_AHRS.bin

You are welcome.
Reminder for IMU330/300 SPI users: from SPI part in online manual

• configurations: IMU working in SPI mode; SPI mode 3(CPOL = 1 (polarity) and CPHA = 1 (phase)); Data is transmitted 16-bits words, Most Significant Bit (MSB) first;
• read and write register sequence:
  
  
• Follow the timing applies at system startup:
  

@Linuxer
pls refer to SPI description, the working process of single read is:
and you also need wait more than 16us after request command, such as: 56 00 request, and 20 us later receive the feedback.

May be already damaged by misoperation, we are trying to find solution for you, pls wait.

"Before installing it, the IMU doesn't output any data such as acceleration, gyro."
when got it from plant, it should be working well. but your unit configuration not right, so after you received before installing IMU, what actions did you do?