Question My materials are not rendered anymore

I opened my HDRP project and found my scene completely empty...
I see the gizmos, and when I click on an object in my hierarchy, I see the outlines of the object.
The layer are all visible, I have checked that.
So I think the problem comes from my materials. In the asset tab, the materials preview is totally black.
I tried changing the shader, but it's only when I change the shader to standard that a pink preview appears. It's normal since it's an HDRP project.
I tried: update HDRP to lower version, remove then reinstall HDRP package, but nothing seems to work...

I really need help, since I can't continue my project anymore.

I should add that before, there was a bug on the builded game where pink and white stripes where coming from the ground...

 

Finally!!! I've been looking everywhere, and it seems that a warning (yellow console error) was saying that HDRP was in conflict with an other version of HDRP. For those who have the same problem. Just go to Package Manager and update to 7.3.1 on 2019.4. It seems that I've updated to 7.5.1, and this not the default version of HDRP. Make sure to update with the correct button at the bottom right, and not with the list of versions that unity provides at the left side.