Why won't iMac user list load, black screen?

Question

macOS

iMac 21" (I don't know which version, was purchased in 2013) boots as usual, but at the moment when you need to show users for selection, a black screen appears and only the mouse cursor is visible.
Reset all hardware settings, performed a disk check. Reinstalled OS X
Nothing helped. Tell me if anyone had such a problem

Answer 1

Try this:
Resetting the SMC and PRAM for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve
• Shut down the computer.
• Unplug the computer's power cord.
• Wait fifteen seconds.
• Attach the computer's power cord.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need them in the next step
• Wait five seconds, then press the power button to turn on the computer.
• Press and hold the Command-Option-PR keys before the gray screen appears.
• Hold the keys down until the computer restarts.
• Release the keys.