Hello Pieter Boshoff,
After removing the camera accessory from the Home app, did you have a chance to quit the Home app and restart your iPhone? That solves a lot of issues, similar to this. If not, let's try that now: Close an app on your iPhone or iPod touch - Apple Support
How to close an app
You should close an app only if it’s unresponsive. The way you close an app depends on the type of device that you have. Find your iPhone or iPod touch model below, then follow the steps. Or learn how to close an app on your iPad.
iPhone X and later
1. From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
2. Swipe right or left to find the app that you want to close.
3. Swipe up on the app's preview to close the app.

iPhone SE, iPhone 8 and earlier, and iPod touch
1. Double-click the Home button to show your most recently used apps.
2. Swipe right or left to find the app that you want to close.
3. Swipe up on the app's preview to close the app.
Then follow these steps to restart: Restart your iPhone - Apple Support
After that, try adding the camera again: Add a HomeKit accessory to the Home app - Apple Support
If the issue persists, how did you remove the camera accessory the first time? What specific steps did you take? What does the error say exactly?
Hoping to hear back, cheers.