Optical Flow PMW3901 problem

Hi everyone. I have a drone with pmw3901, But POSITION HOLD not working.
In MAVLink Inspector I see a data from OF.


But in MAVLink console the output of the dmesg shows some errors and warning related to the optical flow:
INFO [vl53l1x] vl53l1x init success
vl53l1x #0 on I2C bus 2 (external)
pmw3901 #0 on SPI bus 1 (devid=0x6c)
WARN [SPI_I2C] pmw3901: no instance started (no device on bus?)

ekf2 [275:100]
INFO [ekf2] 0 - selected distance_sensor:0
ERROR [ekf2] 0 - optical_flow lost, generation 15 → 17

And…
nsh> pmw3901 status
INFO [SPI_I2C] Running on SPI Bus 1
pmw3901: read: 52987 events, 4624122us elapsed, 87.27us avg, min 86us max 113us 1.434us rms
pmw3901: com err: 0 events
What could be the problem?