Hello Starman1148,
Welcome to Apple SUpport Communities. We understand you need some help with grouping new HomeKit accessories.
Look at this article to double-check the steps being followed to find that option:
Control accessories with Home on iPhone
Then, we'd recommend making sure your devices are fully updated:
Update your iPhone, iPad, or iPod touch
Update HomePod - Apple Support
It can also help to try force closing the Home app, and relaunch it:
Close an app on your iPhone or iPod touch
Restarting your devices can sometimes help with odd issues that crop up as well:
Restart your iPhone
Restart HomePod mini or HomePod
Open the Home app on the primary user's iPhone, iPad, iPod touch, or Mac. On iPhone, iPad, or iPod touch, press and hold HomePod. On Mac, double-click HomePod. Scroll down and tap or click Reset HomePod, then select Restart HomePod.
Take care.