If you removed the home app you will need to put it back by setting it up again.
Are you saying it won’t set up with your iPhone? Check the phone isn’t on lock screen
Try set up again. Make sure you do the “Get Started” sections in Set Up.
Set up and use HomePod – Apple Support
if it won’t set up as instructed then you will need to try a full reset then set it up.
Reset HomePod - Apple Support
- it might also be your phone that's acting up and not connecting to wifi, reset network settings on that and restart your iPhone and check it is updated to the latest version of iOS.