After more than 15 years covering everything Apple, it’s with a heavy heart we announce that we will no longer be publishing new content on iMore and the iMore forums will be closing as of November 1st, 2024.
Welcome to iMore! It doesn't always say, "delivered". Try Reset Network Settings.
Reset Network Settings Settings>General>Reset>Tap Reset Network Settings. You may need to enter your wifi passcode back in afterwards.
Even if you're blocked, you will still see the "delivered". It just doesn't always show. Only way to know for sure is call the contact. Ask.
If you're going on the premise that you'll see "read" on your device next to a message you've sent, then know that not everyone enables the "send read receipt" option on their device. Sometimes, people prefer not to feel the need to respond immediately. If you've indeed been blocked, there isn't anything on your device to indicate it.