One morning I found myself locked out of my EliteBook 850 G5 when at power-on the Power-On Authentication security feature I have did not recognize my simple 4 characters numerical password I was using for many months before that.
I was using 'Power-On Authentication' and 'One Step logon' features and you can see below for exemplification, a screen capture of the Security Features taken from the Internet, with the mention that in my case it was the second feature checked, not Windows Logon but Power-On Authentication.
I want to specify clearly that I did not change my BIOS settings a day before being locked out. I did not change security settings. I did not do any windows reinstall or upgrade. I did not configure a fingerprint or did anything voluntarily to cause this.
I simply found my password, the same one I always use, is not being taken. I tried to use an USB keyboard too, in case my notebook keyboard is faulty - same result.