No Login Prompt on Startup (Login) screen. Completely "Locked-out" of Win10 Home Laptop

This happened to me some time ago on a Insider Preview, nothing to do with using Hello though. I did this:

Select the Power icon in the bottom right hand corner of the screen and hold down Shift and select Restart.

This should give the Troubleshoot menu, next select Advanced options and then Command Prompt.

Enter Command Prompt and enable the built-in Administrator account using the command:

net user administrator /active:yes and press return.

ref https://www.ghacks.net/2014/11/12/how-to-enable-the-hidden-windows-10-administrator-account/

This brought back my sign-in and I was able to continue as normal. Worth a try.

When I hold down the "Shift" button and select the Power icon with my mouse, the Startup (Login) screen disappears for 30 seconds, then reappears without any login prompt. 

All this "crazy cycle" (prompt-less login screen disappears for 30 seconds then reappears without a login prompt) started after installing Win10 v1803 (Redstone 4) and trying the Windows "Hello" PIN login option. Normally I use a "password" to login without any issues with v1803...so far, except now!!

I'm essentially "locked-out" of my laptop. The mouse and most of the keyboard keys are "inop"...cause the "crazy cycle"!!

HERE IS A RECAP OF THE PROBLEM:

I would always press the spacebar to go from the lock screen to the sign-in screen, I assume this just dims the lock screen but doesn't show sign-in or the Power icon. (bottom right)

If this is the case then once at the lock screen do the following:

Press and hold the power button until power off (usually 8 secs ish)

Power on again and repeat above at the lock screen.

Power on a third time and it should start the recovery environment which essentially will get you to where I was trying with my original suggestion.

Select Troubleshoot and then Advanced options then Command Prompt. Enter the command I suggested.

You will also see other options one of which will be the option to Roll back to the previous version of windows (if it's still available).

Post back the result.

Let me clear up some things with my Toshiba P750 (Win10 v1803) laptop and the way I use it at home (right or wrong):

1). I always have AC power connected, only use battery if necessary. Use laptop lid to power down and up!!

2). When the "laptop lid" is raised, the laptop powers up.

3). Once powered on, the startup (login) screen is displayed as follows:

     a). Startup (login) screen with "NO Login Prompt" of any kind.

     b). Power and Wi-Fi icons displayed in lower right corner.

     c). Date and time displayed in lower left corner, with time

          updating.

4). If I depress the "SPACE" bar (by itself), screen goes dark for 30 seconds, then reappears without any Login prompt.

5). If I depress the "Shift" button + select the Power icon (together) with mouse, screen goes dark for 30 seconds, then reappears without any Login prompt. Can't get to command prompt or Start menu.

6). I don't have a "LOCKED" Login screen. I have a Login screen without any Login prompt that disappears for 30 seconds and then reappears without any Login prompt ("crazy cycle") when I attempt to do anything with keyboard or mouse.

7). This "crazy cycle" started innocently a week ago, on 7/29/2018, when I raised my laptop lid to power up and startup (Login) screen appeared without any Login prompts (NONE).

8). The last "unusual" thing I tried, out of curiosity, was to created a unique ("new") 9 character PIN and login with Windows "Hello PIN" and was successful on 7/24/2018. Have Win10 v1803 installed. All normal laptop functionally working.

9). "Strangely", on 7/29/2018, when laptop lid was raised to power on, Login screen appeared without any Login prompts...and the rest is nothing but frustration!!

Hope this helps. I'm trying to give as much detail as possible for a solution is beyond my Windows 10 Update fragile experience. 

BTW, I'm borrowing a friends laptop to conduct my normal daily computer activity.

It sounds like the laptop is hibernating when you lift the lid. Usually the first screen you see is called the "Lock" screen and then you press a key to get the sign-in screen. (that shows the sign-in box)

In my initially instruction I said to select the Power icon, hold down shift and select Restart. If you can't do this then you need to press and hold the physical laptop button until a forced power off. (Usually around 8 secs) Complete the routine I posted earlier.

Neil,

You da man!!  Your instruction to do a "forced" power off by holding down my Toshiba P750 laptop power button for 8+ seconds did the "trick" all by itself!! I could hear my hard drive shut down.

As you mentioned, my laptop was in "hibernate" mode by me using the laptop lid instead of a S/W (soft) power down sequence. I usually operate in this mode because I access my laptop at various hours of the day or night, now that I am retired after 40 years of being a Systems Test and Integration (H/W & S/W) Engineer for Fortune 500 companies.

Once I powered up again with the power button and the "Lock" screen displayed, I simply used the "Space" bar (normally use right mouse button) to display the Login in text box, with the "Hello PIN" option. "Hello" PIN worked and laptop seems fully functional. What a relief!!

Thanks for making the distinction between the Win10 "Lock" screen and "Login" screen. 

Question: Is it advisable to operate in "hibernate" mode for long periods of time? I've done it for years without any S/W repercussions. I've also read pros and cons about always having your laptop plugged into AC power. 

Thanks for your persistent help!!

Glad it worked.

May have been the change you made and the fact it was in hibernate that caused a glitch and all it really needed was to power off fully to get you working again. Hibernate should work as you have been running in the past so just keep that mode for now and see if it happens again.

Here's what I learned. 

In the course of troubleshooting this problem, I "manually" recycled power, numerous times, using my Toshiba keyboard power button, but only casually...not holding it down long enough for a "forced power down" state.  Therefore my laptop was probably still in "hibernate" mode. 

Perhaps, there's any incompatibility between Win 10 "hibernate" mode and Windows "Hello PIN" login process. 

Interestingly, this Win10 combo (Hibernate mode + Hello PIN) worked for me for a couple of days and then went "goofy" on me!!

As I mentioned earlier, I usually Login in with a "password", not a PIN!! I'm just exploring some of these "new" Win10 features, but don't really need them for my daily computer requirements.

My only daily job in retirement (single, never married or kiddios, NO DEBT @ age 73)...is to "manage" my 7 figure, soon to be 8, retirement portfolio...that simple!!

Life is a bowl of cherries, throw out the "rotten" ones!!

Thanks again.