My computer wouldn't boot successfully and was stuck at a screen with the following text:

EFI Shell version 2.10 (4.641)
Current running mode 1.1.2
map: cannot find required map name.

Press ESC in 4 seconds to skip startup.nsh, any other key to continue.

This issue occurred for me because I was recently working inside the case and left a power cable for the hard drive disconnected. So you may be having the same problem if you recently cleaned, moved, upgraded, or anything else that could cause the cables to come disconnected. Check your power and data cables to your hard drive and make sure they're connected.