I was texting someone and they have there read receipts on, and it says it was delivered but not read. Why is that and it still says delivered a few days later but they have not read it yet?

They were sent. That's what "Delivered" means. The fact that it hasn't changed to "Read" means they have have it on their device but have not looked at it yet. Or, person may also have turned off the option to show that they have read the message. I keep that option off on my phone so, if you were to send me a message, you would never see it change to "Read".

Have you spoken to this person and verified that they have read the text and that there is an error? Or are you just assuming that they have read it? In all likelihood, it means exactly what it seems to: they haven't read your text yet.

Note: If they read the message in the Notification Center but never opened the Messages app, they would know the contents of the message (assuming it wasn't too long) but it wouldn't show as read.

Then that means she hasn't read it. Send her another message to see if she responds.

She just may not be that into you, bro.

Do you have some reason to think the "not read" result is incorrect?

It will say Read when she open the Messages app and opens the conversation the text message is in.