When connecting over SSO and adding a display name, a password field appears "intermittently".
As a User types in a name in the Name field Vanilla is doing a lookup to see if that name exists on the forum. If it exists, we assume that the User who is typing is the same User who created this account on the forum. We are offering them the opportunity to put in the password for that account and log in.
The reason it appears to work intermittently is because if a User types in a name that doesn't exist it won't present the password field. Or, if a User types slowly enough and the system can look up a name that is partial match, it will un-hide the password field. As the User keeps typing, the name no longer has a match and the password field is hidden again.
WARNING This workaround works only if you have your SSO to AutoConnect users. That means if the email being passed over in the SSO response matches the email of the account already existing in the forum, you trust that it is the same user and you automatically connect them. In this case, you are only presenting the password field for the purpose of connecting user names. For more on AutoConnect see this section in SSO Overview
To change this behaviour, you can override the CSS by adding this line to either your custom CSS or in Pocket in the Dashboard:
display: none !important;
If you find that you are receiving a "Password required" error but there is no Password field it is because you have implemented this workaround without having your SSO Registration set to AutoConnect.