I had a similar Problem with my pixhawk4. I have also a MS4525.
Try first trough the console (nsh) sdp3x_airspeed start -b x
x was in my case 4 (depends as far I understand which i2C port you are using.
If this is successful then ad on the sd card the file extras.txt and put the command above in this file.
Tim, will be back (in front of a pixhawk not before the end of the month). I just looked in the Web about the sensor I was referring. The command I wrote is not for the 4525. But I am sure the 4525 works with the pixhawk4. We use the 4525 sensor in another Plane with the pixhawk4.
BTW: do you have a scope to see if you see any pulses on the date wires?