Hello Bizzy-Bee444,
You can use the steps below to manage what apps are able to access your camera:
1. Go to Settings
> Privacy & Security.
2. Tap a hardware feature, such as Camera, Bluetooth®, Local Network, or Microphone.
The list shows the apps that requested access. You can turn access on or off for any app on the list.
You can also find those steps in this resource: Control access to hardware features on iPhone - Apple Support
Additionally, this resource covers that process for granting access to your photos: Control access to information in apps on iPhone - Apple Support
Should you continue to experience difficulties with just that particular app, you'll want to follow the recommendations below: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support
1. Close and reopen the app
Force the app to close. Then open the app to see if it works as expected.
2. Restart your device
Restart your iPhone or restart your iPad. Then open the app to see if it works as expected.
3. Check for updates
To see if updates are available for the app, open the App Store, tap your profile icon, then scroll down to see if updates are available. If updates aren't available for the app, update the software on your iPhone or iPad.
4. Delete the app, then redownload it
Delete the app. When you do this, you might lose data that was stored in the app. Then redownload the app. Then check to see if the problem with the app is fixed.
Those steps should help to further isolate an app specific conflict.
If you are still unable to address that behavior, you'll want to reach out to the app developer: How to contact an app developer - Apple Support They'll be in the best position to assist further with their particular app.
Take care.