I uploaded a lot/ a Sim to the gallery but even after a few hours it does not show up there
The most common cause for this is that the gallery filters out lots and households that contain custom content. The gallery has a mechanism that checks if your upload as custom content and then marks your upload as such.
Sometimes stuff without custom content is wrongly categorized as containing custom content. For example are pictures of custom content are also classified as custom content.
Check the box Advanced – Include Custom Content. This will make the gallery show all uploads.
Unfortunately this setting is not saved so you need to re-set it each time you visit the gallery.