Photos won't import pictures from iPhone without a system restart

OK, cool, thanks.

My method has always been to plug in my iPhone through USB, and Photos then says, "I see you have new pictures. Would you like to import them?" (metaphorically speaking)

Now I get a screen that says "Preparing to import photos from RB's iPhone" that never resolves into an actual import process. I can leave it like that for an hour and nothing happens.

This is a brand-new iMac with four of the newer-type USB ports, and I am using the supplied Apple Lightning connector cable. I have tried all four ports, just in case. I have also quit and restarted Photos, and restarted my iPhone, with no success.

The only thing that works is to restart the iMac. I tend to have lots of apps open and multiple tabs in my browser that are a pain to reopen when they involve signing back into sites.

OK, I have stumbled upon an answer. While trying to debug a network connection, I opened Network Preferences. I'm using Big Sur 11.5.2.

There I saw something new: Besides the Wi-Fi network, I saw Ethernet (not connected), Thunderbolt Bridge (not connected) and iPhone USB2 and iPhone USB (both not connected).

I discovered that you can click on the iPhone USB or the USB 2, and uncheck the box that says "Disable unless needed." I did that for both iPhone connections, and when I plugged into the cable — Boom, Photos was able to see and import my pictures like normal.

This is a new "feature" of the Mac OS, so if you have similar difficulties with USB connections, here's a place to look.

Definitely was worth a try. Nothing happened when I opened Music, even after clicking on my phone. I went as far as backing up the phone through the Finder and then running a Sync. Same issue.

More data: Also tried to connect to Photos on my new MacBook Air.

Same exact result.