Hello Zlata5675,
Welcome to the Apple Support Communities!
It looks like you're running into issues with downloading Apple Music for offline listening. If the music went missing before this happened, it may have been related to changes made to the device such as resetting the device, restoring the device, or changes to the Apple ID associated with your iPhone. Are any of these changes something that were recently done?
When you've associated your device with another Apple ID, you will need to wait 90 days before you can change the Apple ID that's being used. Currently there is no way to bypass this process. You can find more details here: View and remove your associated devices for purchases. Scroll down to "More about associated devices" for further info.
We hope this information helps you out.
Cheers!