Apple Music and App Store doesn't work anymore since update to Sequoia

This happened to me, and it seemed related to WIFI because everything started loading when I connected to my iPhone's hotspot instead.

Then I went into the Wi-Fi settings, Network details, TCP/IP, and renewed the DHCP lease. Finally, I reconnected to Wi-Fi, and everything continued to work even after closing and reopening the apps.

I hope it helps someone.

The only other thing I can recommend is to post the free EtreCheck report. This report does not contain any personal information, but will show the processes running on startup and may point to a problem with one that was migrated from Sonoma and now not compatible with Sequoia. Use the Additional Text option when posting.

How to use the Add Text Feature When Post… - Apple Community

I can say both open fine for me on Sequoia. Each opened with a message highlighting new features and Apple Music has a message for about 10 seconds saying it was updating my iCloud library, but both work fine.

I suggest starting up in Safe Mode and try again, then restart normally. Safe Mode will do some cleanup while starting up that may be necessary after the update.

1. On your Mac, choose Apple menu  > Shut Down.
2. Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.
3. Press and hold the power button on your Mac until “Loading startup options” appears.
4. Select a volume.
5. Press and hold the Shift key, then click Continue in Safe Mode.
6. The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar.