Thanks for the info.
First thing, all devices send data on certain channels, 1-16 (or in terms of the midi data, 0 - 15). Receiving devices may be set in different ways, but they may receive data on certain channels as well. If you send data on Ch 1 (because that's what the keyboard defaults to), but the receiving device is set to Ch 2, then the receiving device will see that data is coming in, but will not 'play' it as it's on the wrong channel. On the basis of what you describe, this MIGHT be what's happening here.
Try to see what Channel the data is set to on the sending device. Check the manual for the receiving device and see what it defaults to, and try to be sure they are BOTH using the same channel. Or channels, your sequence could have data on more than one channel at the same time.
Why are these things so fussy? Think of performers who may have a big sequence and many keyboards. Each keyboard can be set to receive data on just one or two channels, so the data from the sequence may all go to all keyboards, but only the correct keyboards will take notice of their part, and will disregard the rest.
You might find it a help is you could create a sequence that sends a few notes on EVERY channel, i.e. 1 thru 16. Make each channel a different instrument. Then see which ones actually 'sound'.
Many keyboards may have default settings, and without being told, they will 'hear' data on that channel ONLY.
Geoff