Using Voiceover at login screen
With no concrete details or info whether you’ve gone through troubleshooting and can reproduce this after a reboot, here are some triage steps. 


Check the voiceover guide to you know which key shortcuts can start the speech: https://help.apple.com/voiceover/info/guide/10.12/#/vo2755
Restart the Mac and go through the basic steps once you are logged in to a new test account - https://help.apple.com/voiceover/info/guide/
Once you’re sure voiceover is working in the new test account log out to the home screen and retest.