Chosen Solution
When startup, the loading bar reach 70%. The monitor turns to save mode and blank screen. Press monitor power button. Turn off and then turn on again. The login screen is appeared. How to fix it? 更新 (2019年07月01日) cannot fix the issue.
First try starting in Safe Mode to see if you have extension issues. Boot up holding down the Shift key. Next see if you can boot to the repair portion. Hold down the Option key on boot and see if you can select the Repair Partition. If you can, then run Disk Utilities.
