Thanks for contacting sling forums!
The second remote is probably an RF (Radio Frequency) device. The IR Blasters need to be used with an IR (Infra-Red) remote. The IR Blasters will need to be set up on the second box if it has an IR eye. You will need to contact DISH and ask how to change that remote to IR. The Slingbox needs to be at the box used and plugged to Slingbox.
Hope this helps!
Sling Moderation Team