This is typically caused by outdated mods. Please see this thread for more information: https://answers.ea.com/t5/Mods-CC-Issues/MOD-RELATED-Sims-disappeared-from-household-Blue-flashing-square/td-p/8428174 The only fix is to revert to an unaffected backup save. Here's how to load a backup: https://sims4.crinrict.com/eng/2014/09/recover-backup-save-game/