apple music songs won't play offline

Hi there, mhmdheikal8.

I see that you've started a trial subscription to Apple Music. The issue is, songs that you've downloaded to your iPhone 6s on iOS 11.2.6 is saying that the content isn't authorized. Great job on the troubleshooting you've completed and I'm happy to help.

Add and download music, shows, and movies from the Apple Music catalog -- When your device isn't connected to the internet, you can play the songs you'd like from "Downloaded Music".

Before you add or download content, make sure to turn on iCloud Music Library on all of your devices.

When you add content to your Library, you can access it across all of your other devices, as long as you're signed in to all of your devices with the same Apple ID.

You can also download content to your iOS device or computer so that you can listen to or watch it when you're not connected to the Internet. You must download the content to each device that you want to use for offline listening.

There's no cost to add or download content. Learn more about Apple Music and how to join. If you don't subscribe to Apple Music or want to purchase an individual song or album, you can buy it from the iTunes Store app or in iTunes on a Mac or PC.

Turn on iCloud Music Library -- If the issue persists, make sure that "Show Apple Music" is turned on in Settings > Music.

Turn on iCloud Music Library

Make sure that you're signed in to all of your devices with the Apple ID that you use for your Apple Music subscription. Then follow these steps to turn on iCloud Music Library.

On your iPhone, iPad, or iPod touch

1. Go to Settings > Music, and tap iCloud Music Library to turn it on.
   
   
2. If you already have music on your device, you're asked if you want to keep the music that's on your device.
   If you choose Keep Music*, the music from your device adds to your iCloud Music Library.
   If you choose Delete & Replace, the music on your device is replaced with the content from your iCloud Music Library.

Thank you for getting back to us with that information, mhmdheikal8. It's appreciated. Since you're still experiencing the issue I'll focus on the Music application next.

How to force an app to close on your iPhone, iPad, or iPod touch -- First, force close Music application if it's open, then -- Restart your iPhone, iPad, or iPod touch -- Restart your iPhone. Once it's returned to the Home screen, test the issue.

How to back up your iPhone, iPad, and iPod touch -- If restarting your iPhone didn't resolve the issue, please be sure to have a fresh backup to keep your personal information safe. In order to back up your Health data, the backup needs to be encrypted. iCloud does this automatically, but iTunes doesn't. If you'd like to use iTunes to back up your iPhone, refer to this article: About encrypted backups in iTunes

If you can't update or restore your iPhone, iPad, or iPod touch -- Even though the title of the article isn't specific to your issue, the section titled "Put your device in recovery mode and set it up again" will walk you through all the steps to reinstall the iOS software on your device. Test the issue once again.

Let me know how that goes.

Take care!