I had this same issue, where Cubase 8 just mysteriously stopped starting up at all.
Version: Cubase 8 (64-bit version)
Operating System: Windows 10
USB dongle: Mbox first generation (literally the first one model ever made I believe, the “Product” and “Model no.” on the bottom both just say “MBOX”, it is OLD, but still works fine with garageband, so I figured it’d work with Cubase)
Was able to record just fine for a while, then one day I went to open it and it just… wouldn’t. Unlike yours, my task manager didn’t show any Cubase instances open in the applications or processes list. Swapping or unplugging the USB interface did nothing. Like you, I’d recently installed Daemon tools and a few USB drivers. Specifically, Avid Mbox driver 1.1.10 and ASIO4ALL v 2.14, and maybe another in my flailing attempt to get my Mbox working. Weirdly enough, that combination worked fine for a full day. It was only the next when it mysteriously locked up. The steps I took:
- Restarted computer (no change)
- Restarted computer with updates (no change)
- Uninstalled Daemon tools (no change)
- Uninstalled all audio drivers and reinstalled only the factory drivers for the computer (no change)
- Uninstalled Cubase and reinstalled it - This fixed Cubase’s inability to boot up, though then of course my USB interface (Mbox) no longer worked.
Trying a new approach, I did the following:
- Uninstall Cubase
- re-install my Mbox drivers (ASIO4ALL and Avid Mbox)
- Re-install Cubase (and update)
Still no start, with nothing showing up in the task manager. Not sure what’s going on, but it seems to be something to do with the USB interface driver.