Final answer:
The tile that will not display in the Windows 10 Action Center on desktop computers is the Rotation lock, as desktops do not have the necessary hardware for screen rotation.
Step-by-step explanation:
The sales personnel in your question use Windows 10 computers, and when they are using their desktop computers, the tile that will not display in the Action Center by default is the Rotation lock. This feature is typically available on devices with accelerometers, such as tablets, that can be physically rotated. Since desktop computers are not designed to rotate and do not typically include these sensors, the Rotation lock tile is not shown in the Action Center for them. Other tiles like Tablet mode, Connect, and VPN will still display, as these functions can be relevant to desktop usage as well. Tablet mode can still be engaged on desktops for a more touch-friendly experience if the display supports touch input. Connect is used for connecting to wireless displays and devices, and VPN is used to establish a secure connection to another network over the Internet.