Went a Firmware Password has been enabled on the computer
Refer to the link provided by my colleague @den.thed for details
It, the Firmware of the computer will not allow booting to the Normal Password Screen
You must manually input the Firmware Password you had chosen when it was enabled
Normally, the Firmware Password is Not the same password you would normally use at the normal log in prompt
If you do not know the Firmware Password or have forgotten it or have not written it sown and kept it ?
From that same link provided by @den.thed
" If you forgot the firmware password "
If you can't remember your firmware password, schedule an in-person service appointment with an Apple Store or Apple Authorized Service Provider. Bring your Mac and its original receipt or invoice as proof of purchase. "
There is not other way to get around this