manually managing music on my iPhone isn't working

I have macOS Sonoma, iOS 17.

I like to manually manage music on my iPhone. I do not want to Sync or put music into iCloud because I need lossless music files on my iPhone.

So when I connect my iPhone 12 to my MacBook, I go to Finder and find the setting "manually manage music and videos..." and check it. Two buttons appear in the lower-right corner... Revert and Apply. I click Apply and a warning message comes up that says "Syncing" this iPhone will replace media. I click cancel because I don't want to sync the the iPhone. By the way, in the music tab I do not have Automatically Sync checked.

After I click cancel, if I click away from the iPhone in the Finder and click back to it, the "manually manage music" checkbox is no longer checked, as if the setting was not applied.

In the Music app, when I try to drag and drop mp3 files onto my iPhone, they bounce off.

So what's wrong? Why can't I drag music files to the iPhone?