Hello pfreader_apple,
First off, congratulations on your iPhone 12! We see you're encountering some issues with several apps on your iPhone 12 thinking your device isn't online, though you're able to use other apps, and browse the Internet. We definitely understand wanting all your apps to function properly and have full access to the Internet, so let's see how we can help get this rectified.
To begin, does this occur all the time with these specific apps that were listed, or are you able to use YouTube/Facebook/DoorDash intermittently? Does the issue occur with any other apps, or occur with Apple apps?
Also, are you only encountering issues with these apps using Wi-Fi, or have you encountered the same message while using cellular data?
We have several steps that we can attempt, such as checking for app updates, restarting your iPhone, and reinstalling the apps, if needed. Please review the following article, beginning with the 2nd step:
If an app unexpectedly quits, stops responding, or won’t open
If the issue is only occurring with third-party apps, you may need to contact the app developer(s) using the steps at the bottom of that article.
We're confident that those troubleshooting steps should help resolve the issues you're experiencing.
Cheers!