Good afternoon WO_VENOM,
Welcome to the Apple Support Communities!
I understand you have updated your iPhone to iOS 13, but are unable to access the Camera app when using Snapchat. I have a few steps you can try to address this issue.
- First, check to make sure you have enough available storage on your iPhone - How to check the storage on your iPhone, iPad, and iPod touch
- If it appears that you have enough available space on your device, the next step is to update the iOS. On September 27, iOS version 13.1.1 was released. If you haven't already done so, please update to that version - Update your iPhone, iPad, or iPod touch
- Restart your iPhone, and then see if there is an update to the Snapchat in the App store - Update apps or use automatic downloads
- Open the Snapchat app and try to access the Camera app.
- If the issue persists, check the privacy settings for your Camera. Open the Settings app > Privacy > Camera. Apps that have requested access to the camera will appear here. Do you see Snapchat listed? If so, enable Snapchat in the privacy settings.
- Check the Snapchat settings as well - Open the Settings app and select Snapchat. Do you see the Camera app in the section "Allow Snapchat to access" list? If so, enable it.
If the issue persists after trying these steps, you may need to contact Snapchat for additional help with their software, including clearing the cache - How to contact an app developer
Take care.