Hey again @tmaughan
Sorry for the delayed reply
Been able to test this under a Win 10 Pro x64 machine running Live Suite 10.1.15 and Kick 2 v1.1.4
Same results when dropping your file onto a click slot inside Kick 2, no waveform displayed and no sound.
Same weird behavior since I am also able to preview the sample from Live's browser and drag & drop it on an empty audio track inside Live also works as expected.
I've checked Live settings under Windows as well and it's also possible to set AIFF as "File Type" under the "Record Warp Launch" Preferences Tab.
After dragging your sample onto an empty audio Track, I consolidated it and export it back outside Live.
Then I tried to load it back onto a Kick 2 Click slot and it worked.
Here's the converted file from Live, with Audacity you should be able to export to AIFF format selecting --> Export to Audio File --> Other format.
Converted Deepie_single_kick.aif (84.1 KB)
So definitely something weird with those audio samples, not related to Kick 2 and AIFF files import.
Best solution is to convert those audio files either to AIFF again or WAV then you should be able to use them as clicks with Kick 2.
Hope this can help