Did you install the mod correctly?
Not too deep? Took it out of the archive?
What's your version of The Sims 4?
The mod comes packaged in .zip archive, which you need to take it out of in order for the game to read it.
Check out this page, make sure you've followed all steps to the dot, especially Step 5. as that's what I guess might be wrong: https://wonderfulwhims.com/installation/