I have finally decided to upgrade my macs to Mojave from High Sierra. For my work machine however, VirtualBox simply stopped working and throwing
NS_ERROR_FAILURE on startup. Similar to this. Trying to reinstall won't work because the installer will fail at the last step.
I have tried everything suggested from disabling Gatekeeper to many many iterations of uninstall/reinstall. Almost every solution suggested clicking
Allow on the Security & Privacy tab but it never appeared.
What worked for me finally was: macos - VirtualBox 5.2 Won't Install on Mac OS 10.13 - Ask Different which boils down to:
Go into recovery mode (reboot with Cmd + R during loading screen) and open the terminal:
spctl kext-consent disable spctl kext-consent add VB5E2TV963 spctl kext-consent enable reboot
That is basically the
Allow part which will finally make the install successful.
VB5E2TV963 is the Oracle id that we are allowing.
If you are in similar situation, I hope this will help.