I had the same problem with my Medion computer.
Go into Device Manager and look for a device that is not digitally signed.
You have to remove the driver on it and download one that is digitally signed or change the file or folder to allow it.
Took me about a week to work out how to allow it.
Microsoft does not like unsigned drivers and this is the result.
Sorry if I am a bit vague but it happened to me a few months ago and have since reset the computer to factory settings because of a different problem.
I now remember that I had to change the File to allow the driver but not sure how I did it.