I found a couple of issues with your CAD model. First, if you look at the Mesh Event Log, The last line in the image shows the Area of the Smallest Face which is 5.7e-11m. This is very small.
When I looked at your model in Onshape I found about 15 curves with a length less than .1mm. In the image below you can see a blue dot on the curve of the fillet. That blue dot is actually a curve with a length of .056mm. The fillet curve is made up of three separate curves.
Finally, without cleaning up your geometry I was able to mesh your model with a Parameterized Tet mesh. The setting are shown in the image below. As you can see I had to set the minimum element size very small.
It would probably be best to use Catia to find the small edges and to fix them in CAD and then re-export your STEP file. You can use the brute force method that I did, but it is going to be a really large model.