The game's aging manager is known to be fragile. Is it only the active household that is refusing to age (could be an outfit problem) or all sims in town? You could try switching aging off in the Game Options, play for a while, then switch it back on again. But often enough there is no solution without mods other than moving your sims to a new game.
NRaas Overwatch and StoryProgression's aging managers are much more reliable in this regard, for those using mods.
But if the game is operating on a drive that lacks sufficient free space (35 GB free or 15% of the drive, whichever is higher), or is suffering from some other kind of drive related issue, then all kinds of misfiring can happen and the game just won't function properly.