Viewer Non-Delivery Issues
This video explains VIEWER-RELATED non-delivery issues in Second Life. This information applies to ALL deliveries - from both individual people AND scripted delivery systems - and, if the affected viewer(s) are used on multiple grids, then all grids they are used on as well - not just those from any specific vendor maker!
If the customer is on a V3-style viewer, they need to look in their upper right (or lower right if they're on a really old version) and click the object icon to get the delivery popup back. This icon is shown in the image below, just follow the yellow arrows: