OK so I just fixed Bowling Night Stuff and it was surprisingly easy. Maybe try doing this before resorting to a factory reset if you’re still having problems with My First Pet Stuff.
1) Quit the game
2) Hold the power button down on your XBox for 10 seconds until it shuts down
3) Remove the power cable from the back of the console. It’s the one on the right.
4) Wait for 2 minutes and then plug it back in.
5) Turn your XBox back on
6) Check in Manage Games and Add ons to make sure the pack is listed as installed
7) Restart the game
Thankfully this worked to fix Bowling Night Stuff for me. It is now listed as Owned rather than Download to use on the home screen. I got the pop up on the home screen introducing Bowling Night Stuff, which didn’t happen before.I have loaded the game and took my family to CAS. They have new clothing items etc for the pack so I’m pretty sure it’s installed properly now. Give it a go and let me know if you can get yours to work that way. If not I’ll explain how to do a factory reset.