Arvid,
Check out and complete the steps found in the guide page here If you have problems playing music on Mac and quoted below.
"If the progress bar at the top of the Music window is moving, but you don’t hear anything
- If you’re using your computer’s built-in speakers: Make sure the volume controls are not turned down. Check the control at the top of the Music window and check the computer’s output volume (in the Sound Output settings). See If you can’t hear sound from your Mac speakers.
- If you’re using powered speakers connected to your computer: Make sure the powered speakers are properly plugged into your computer’s audio port, plugged into a power source, and turned on. Also make sure their volume isn’t turned down.
- If you’re trying to listen to music through remote speakers using AirPort Express: Make sure the remote speakers are selected in the AirPlay pop-up menu
at the top of the Music window, and the volume control on the speakers isn’t turned down.
If you’re using an AirPort Express, you can find more troubleshooting information in the documentation that came with your AirPort Express, or at the AirPort Support website."
If you feel the issue is related to your connection, be sure your router meets the recommended settings found here: Recommended settings for Wi-Fi routers and access points
Should the issue remain, test downloading the content (while on your mobile hotspot connection) to see if the playback works as expected.
Add and download music on Mac
Also, does everything playback as expected when using only the cellular connection on your iPhone? What if using the Wi-Fi network only? Checking can help you further determine if the issue is network related. Keep us posted on what you find.
Best.