She purchased a second license, using a different email, but we have not received a second license. What should we do to resolve this?
Just send an email message to shelltools@rttsoftware.com with the order information (order ID if you have received it, buyers name, email address and date of the order), requesting the resend of the license registration email.
Is there a way to purchase multiple licenses at once when paying? There doesn't seem to be a way to change the quantity ordered from its default of 1.
No. But, if requested, I can send a PayPal invoice with the desired number of licenses, or similar solution for the Avangate service. The request should include the end-user personal name, and respective email address, for each of the needed licenses.