@SandraCristinaCB It's strange that all the sims would go invisible at the same time; usually there's only one affected sim, or a few at the most. You can try NRaas DebugEnabler's Fix Invisible Sims command: click on the admin building (it stands in for City Hall) and select NRaas > DebugEnabler > Fix Invisible Sims. If that alone doesn't help, click on your sim and select NRaas > DE > Fix Homeworld. Edit: never mind.
Let the game run for a few sim-minutes, use "save as" to rename the save (so the original remains as a backup), quit, delete the five cache files in your Sims 3 user folder, reload, and see whether the issue is gone. For reference, the cache files are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
You can run a more intrusive reset with NRaas MasterController: click on the admin building and select NRaas > MC > Town Settings > Reset Everything. All sims will be reset, essentially rebuilt using available data. If the DebugEnabler commands alone don't work, it may be worth trying an MC Reset and then running the DE commands again.
Just in case you're not aware, many DE interactions are undocumented and shouldn't be used. They were left in the game by developers, but even the modders don't know what they all do. So it's best to only use commands with well-described effects.