how to tell if your bootloader is locked?
474731
Open the dialer in your phone, and enter the code below. The command will open a new window. Choose Service info > Configuration and if you see a message saying Bootloader unlock with a 'Yes' written against it, it means that the bootloader is unlocked.
45817
Press and hold the Power/Lock Key (on the right side of the phone) and the Down Volume Key (on the left side of the phone) at the same time. When the Factory data reset screen appears, release both of the keys. Use the Volume Keys to highlight Factory data reset, then press the Power/Lock Key to confirm.
1403451
['Hold down the Power key for a few seconds to turn off the smartphone.', 'After that start pressing Volume Up and Power buttons together for a couple of seconds.', 'Release all keys when you see information about Boot Mode.', 'Now select Recovery.']
997377
From the msconfig dialog, open System Configuration. In the Boot tab, select Safe Boot (Minimal), and then select OK. You'll be prompted to restart your device to enter Safe Mode.
263248
Press and hold the Power and Volume Up buttons for 10-20 seconds. The device will restart and go through the boot-up sequence. Note: The forced restart does not delete any data stored on the phone.
527410
['Disconnect external devices.', 'Turn off Link State Power Management.', 'Update available drivers.', 'Run System File Checker.', 'Check malware and virus.', 'Disable fast startup.', 'Restore to previous state.']
1474615
In the Boot tab, select Safe Boot (Minimal), and then select OK. You'll be prompted to restart your device to enter Safe Mode. To exit Safe Mode, open System Configuration. Then in the General tab, select Normal Startup, and then select OK.
146673
['Press the Windows key + R on your keyboard, or by searching for "run" in the Start Menu.', 'Type "msconfig" and press Enter.', 'Open the "Boot" tab in the box that opens, and uncheck "Safe boot." Make sure you click "OK" or "Apply". This will ensure your computer restarts normally, without the prompt.']
305644
['Press and hold the Power key.', 'Tap Restart Now.']
407109
['Restart your computer and wait for the splash screen to appear when it is starting back up. Start tapping the "F"8 key once every second or until you see the "Windows Advanced Boot Options Menu" appear.', 'Choose the type of Safe Mode for your situation. ... ', 'Open your antivirus software and run a scan of your system.']
620524
['Right click Windows Start menu and choose Settings.', 'On the Settings window, scroll down to find and click Update & security.', 'Switch to the Recovery tab and click on Restart now under Advanced startup.', 'Select Troubleshoot > Advanced options > UEFI Firmware Settings.']
369294
['Press and hold the Power button.', 'Tap Restart. The device will restart in standard mode.']
764751
['Press and hold VOLUME_UP button.', 'Plug USB charger (still holding the button) and wait few seconds.', 'Press VOLUME_UP once or twice to select "Normal boot"', 'Press VOLUME_DOWN (for OK)']
1364825
["To protect user's systems from malware attacks, ASUS motherboards implement the Microsoft Secure Boot feature by default. ... ", 'Step 2: Enter the UEFI Ez Mode, then press F7 to enter Advanced Mode.', 'Step 3: Enter the Advanced Mode Menu->Boot->Secure Boot.']
870665
['Use the Windows + R keys to pull up the Command Prompt.', 'Type in “msconfig” and hit Enter to display the menu.', 'Choose the “Boot” tab.', 'Uncheck the “Safe boot” box if it is selected.', 'Restart your computer.']
320062
['Boot from the original installation DVD (or the recovery USB)', 'At the Welcome screen, click Repair your computer.', 'Choose Troubleshoot.', 'Choose Command Prompt.', 'When the Command Prompt loads, type the following commands: bootrec /FixMbr bootrec /FixBoot bootrec /ScanOs bootrec /RebuildBcd.']
25356
Make sure you have a good USB cable and are plugged into a good port. This was always the problem I experience when using ADB and fastboot. Also make sure you update and have the latest ADB drivers.