Did you get a modified gameconfig? You need one to run mods.

With the latest version of the game, the casino exterior will not load, and it appears as a giant hole for that part of the map. It does, however, not drop into the void because it is using the original casino hitbox. What does work are the new Diamond Casino props including the fake casino interior that is visible from the outside.

If I use nothing but an updated gameconfig, everything works fine. But, even adding a few simple things to the update.rpf such as carcols, carvariations, handling, vehicles.meta, and popgroups result in the new exterior vanishing leaving nothing but a hole.

I have replaced countless times with a reinstall:
the update.rpf
mpvinewood (the dlc update)
and even x64p.rpf which contains pieces that the casino should be replacing.

Even if you don't know an immediate solution, I could most likely figure it out with just knowing where the files for just the exterior map pieces for the new casino are located and the files in the update.rpf that are responsible for loading it in (or any files that would load it in).

Here are the pictures of what it looks like:
https://imgur.com/pT8CvI8
https://imgur.com/yhwTX5j

EDIT: You can note in the second picture that the lower LOD for that piece of the map goes missing entirely as well. It could be another map piece that might be disrupting the casino, even though other pieces are fine up close.

The game not loading is Menyoo's fault. Change your Menyoo version to 1.0.0. As for gameconfigs, I can't seem to get them to work, but my game does start.

UPDATE:

This is the closest thing that I could find. While it doesn't detail the specific changes to the update.rpf, one could easily deduce what has been changed with the list. http://www.allpatchnotes.com/patch-notes/gta-v-1-46-patch-notes-updated/

I hate rummaging through the file while trying to find what was updated so I can keep my modified files.

@EastCoastShepard Make sure that when you export your vehicle, it has the same name as the name you assigned it on the sidebar. If they don't match, Zmodeler will export a blank file.

Sometimes scripts add functions that the maker didn't say anything about. For example, one of my scripts sets the "Insert" key to refresh the game which is a nice feature.