Looks like you are on a Mac so my advice is restricted since I am a PC guy.

But, the Apple DLS appears to be a "soft synth". As a result the early question in this thread may apply to you.

"...Have you fixed the ability to send midi via "outputs chords" to the TC Helicon device AND use an internal softsynth like Coyote Forte at the same time?"

This question was never answered here, so I assume the answer is No. Which means you can not send Midi to your Apple DLS and to the VL3 at the same time. Which explains why you are not seeing any blinking lights for midi input on you VL3.

The Video I provided explains this issue and the fix as it applies to a PC.

BIAB – 2025, Reaper (current), i7-12700F Processor, 32GB DDR4-3200MHz RAM, 1TB WD Black NVMe SSD, 2TB WDC Blue SSD, 1TB WD Blue, 2 TB SK NVMe, 6 TB External, Motu Audio Express 6x6