My pets won't age up

Do you have any mods or custom content (CC) in your game? Could you test without?
You can just move the folder to a location outside the Electronic Arts folder.
If the game works without your CC and mods in, your issue is probably caused by a broken mod or CC.
You can find a full list of broken/incompatible CC and mods since game updated on November 13th over here:
https://forums.thesims.com/en_US/discussion/950909/broken-updated-mods-python-terrain-update-get-famous-nov-18/p1

This update, updated the coding for mods so most mods need updating.
If it still doesn't work I suggest taking out half of your mods and CC and testing the game. Then keep splitting until you find all that is broken.
Either update or remove the broken CC/mods.