Simple is what I'm leaning towards as well....
Are the texture's dimensions a power of 2? -and not too large?
If not, and you're absolutely sure the directories are correct, and the references
TO the directories are correct (within the QC
AND VMT files, then it might be a bad model, or a bad compile with an incomplete QC (including an unfinished $keyvalue or "quoted" value).
Try this: You've made successful models before with custom textures, yes? -Rename an old working custom model texture you've used to what the b0rked model now references, and place it in the proper directory. -Test and see if model shows it.
Likewise, also test this: Rename the texture in question to a previous custom working model, place it in the proper directory relative to that older working model and see if it shows up on that model (however bad it may look

)
Otherwise, unless the SMD exporter is outdated or messing up, these issues do tend to be rather simple fixes. -At least in my experience.
[UPDATE]: I forgot to look at your posted QC files,
Ok, one thing stands out to me for the "polevaultpad" for the $body studio keyvalue, shouldn't that value, also include the extension? i.e.:
$body studio "polevaultpad.smd"
I see that for the "goalpost1" you didn't include it, and it is working, and for every model I've made, I always am sure to include extensions for the referenced file names. So That may affect it, may not. I'm not sure, but that's too easy to try than not to test it! Good luck.
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