lilyalle Please go to ea.com, sign in, open Account Settings > Payment and Wallet > Order History, and find the purchase. Let me know what status you see: Completed, Processing, or Failed.
If the purchase is showing as Completed, please make sure it's also listed as owned in the EA App, under Sims 4 > Manage > Manage add-ons. If it's there too, close the EA App and kill the EABackgroundService in the Task Manager's background processes list. Open [install location]\The Sims 4, here by default:
C:\Program Files\EA Games\The Sims 4
Delete the EP19 folder, restart your computer, and clear the EA App's cache:
https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/
and reinstall the pack, then see whether it loads in-game.