There are several causes for users not receiving a message with the username and password after adding users to BBNC from EE. Please check all of the following in order: 

The user has an existing user account. A welcome email will not be sent to existing user accounts. The utility will send the welcome email exclusively to new accounts that it creates while running.
The user was not included in the query. A query can be used when running the utility, and if the user is not in the query then they will not be added and receive the welcome email. 
An email type was not specified when the utility was run. An email type must be specified when running the add user utility, to determine what type of email addresses to use to send the message to. If no email type is specified, no emails will be sent and the message will show as no valid recipients in the NetCommunity message report.
The user does not have an email address on their record with the same email type specified in the utility. Open the user's record in EE, and verify that an email address is listed for the same email type that was used when the add user utility was run. 
The email template option that is selected says Do Not Send Email. If the Do Not Send Email option is selected for the template drop down field, then no message will be sent. 

The welcome message cannot be resent. A separate message will need to be sent with usernames and passwords from NetCommunity