Since you saw it break on multiple tenants simultaneously, I’m guessing this has something to do with the Legacy Lock API migration that’s currently taking place.
http://community.auth0.com/t/auth0-legacy-lock-api-disabled-grace-period-available/12949
A quick fix for now could be to toggle the Legacy Lock API migration in the advanced settings of your tenant.
As to the point of Passwordless Lock, that library has been deprecated. Lock v11.2 and up support Passwordless. You can check out the migration guide at https://auth0.com/docs/libraries/lock/v11/migration-lock-passwordless.