Based on your comments about the optional 56K IR detector, I'm wondering if you may be misunderstanding how some aspects of the USB-UIRT work. The optional 56K detector as well as the 36-40K detector are not used for learning at all. Learning is accomplished with the aid of the wideband IR photodiode frequency detector (see image below).
The wideband frequency detector has a very short detection distance - you must hold your remote about an inch from the detector. The wideband frequency detector, as previously mentioned, is only used for learning. The codes learned must be captured by the host software via the UUIRTLearnIR function of the USB-UIRT API and stored in your host software's database. The host software must be able to pass the stored value to the USB-UIRT via the UUIRTTransmitIR function for transmitting using the 2 high powered infrared emitters.
The 36-40K and the optional 56K detectors are used only when you want to receive codes from the remote controls you already have and you want the USB-UIRT to react to these remotes via the UUIRTSetReceiveCallback function of the API. The UIRTSetReceiveCallback function is only used to detect what action was performed on your existing remote. It does not "relay" the received code but only provides a unique identifier for the received code. How the unique identifier is utilized is determined by the host software.
With all of this said, I am not familiar with the host software (Elve software) you are using so I have no idea how it is handling the USB-UIRT API functions. I would suggest you go back and try LrnHelper again. Hold your remote about an inch in front of the IR photodiode frequency detector, click the "Learn an IR Code" button and then press the button on your remote control you want to learn. Your learned code should appear in the "IR Code (Pronto Format)" text box. Once you have learned code in the text box, the "Test Transmitt IR Code" button should become active. Click this button to transmit the code and see if your hardware responds.
You may have knew this stuff already, but I want to make sure we are singing off the same sheet of music.