[MPU9250] Verify that the DMP is loaded and running

Hi everyone,
I am trying to write python code to make the MPU9250 work correctly. I can't use the SDK at all, so I have to write every function by myself. I'm trying to load the MPU so I can read the 6 Axis Quat directly from the FIFO. I'm trying to "reverse" engineer the sdk so I can understand what is the correction sequence of register I have to initialise. I have a hard time debugging what I am doing. Basically I'm not even sure if I loaded the DMP correctly. I can write it all to the memory, then re-read all of it without any problem. So I believe it's added correctly to the memory. I also set the start address to 0x400. Still, nothing comes out of the FIFO.

Is there any way to help understand what would be the potential problem? (example, a way to confirm or not if the DMP is working)

edit: Just to add more information, I want to initialise the dmp to ONLY receive the Quat. I don't need anything else.

Thank you very much