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
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.