Blank screen on admin pages

Hi there

I need some help. I have a very unique error that we haven't had before:

We have a multisite setup domain1.com. We also have a few sub-sites running eg. domain1.com/site2, domain1.com/site2.

Something happened, but I am not sure what. When I log in as admin on domain1.com/wp-admin, I get a white screen. even the network screens are blank.

When I log in as admin on domain1.com/site1/wp-admin or domain1.com/site2/wp-admin, it all works fine. It is as if my main dashboard is broken, but for all the sub-sites it is still working

Does anyone know what this could be and how to fix it?

I have renamed my plugins and theme folders, but that didn't fix the problem. Any help would be appreciated here

Thanks