Can no longer install VirtualBox

Hi,

I've been using VirtualBox 6.1.12 up to a few days ago, on my Mac Pro 2013 with High Sierra 10.13.6. After trying to install VB 6.1.14, I received an error message leading to kernel protection.

I tried everything to make it work, with no success. The Allow button didn't appear in the Safety control panel. I manually allowed it via Terminal with the "kext-consent" command (Oracle was allowed, but still VB didn't start). I cleaned all the caches, went to Recovery mode to clean the kext cache and the StagedExtension folder. Nothing.

I tried to downgrade to VB 6.1.12, but this one could no longer be installed, still for kernel protection reasons. When I copied the VB 6.1.12 kexts from a TB backup (booting from an external drive), the Mac removed them when booting again from the main drive.

This issue is ongoing, but there is no solution offered in the VirtualBox forum. Maybe someone can help letting me understand if there is some trick on the Mac, to have those kexts be allowed?

Thank you!

Paolo