I was having this problem with AkinaV and French Riviera V and I found a fix for those.

I changed the content.xml to match what YHWHDios wrote, and changed the line

<filesToEnable  />

to

<filesToEnable>
<Item>dlc_akinaforv:/%PLATFORM%/levels/gta5/akina/akina.rpf</Item>
<Item>dlc_akinaforv:/%PLATFORM%/levels/gta5/akina/akina_metadata.rpf</Item>
</filesToEnable>

The Same fix worked for the French Riviera map, I just added an item for every .rpf.