To resend eTickets currently, you will need to click Resend Tickets from each sales order record, as seen below.

Email Tickets

If you would like to see bulk eTicket sending become available in Altru, please vote on this Community Idea located here: I encourage you to vote on this post as this is an opportunity to have a voice in the product development process. Our Product Management team uses a variety of methods to determine new features in Altru, and the ideas in the Community is one way they do this, so your vote helps Product Management prioritize the new features that we put into the product.