Yes, the RS 15-2116 remotes are too old to be able to send the Cisco IR signals. Nearly all learning remotes struggle to capture those signals (the XMP protocol).
If you really want to continue using the 2116 remotes, you can buy a
USB interface cable and JP1 adapter (together $39). There's
free software which will allow you to upload an upgrade for the Cisco box to the remotes. The upgrade file already exists, so it is very easy to do the upload. If you have Blu-ray players or other recent equipment, the interface cable will allow you to incorporate those into the 2116 also.
Or you could buy the RCA RCRP05B for $15-$20. It's made by UEI, the same company that made the 15-2116, which means it is a reliable remote. Use setup code Cable 1982. Of course it will handle Bllu-rays, etc out of the box. It's a 5 device remote.