Syncing photos from my MacBook Air to my iPhone 11.

Later this afternoon I was able to run your theory by an Apple advisor. He said once the iPhone is connected to the Mac (via the cable) the battery is no longer involved. The phone is getting its power from the Mac. Perhaps I didn't explain what I was trying to do well enough in my first post. The advisor walked me through removing the entire folder from my phone, then adding it back to my phone with the new additional photos. Although not an elegant solution, it worked!

I just updated the software on both the iPhone & Mac to 18.6 and 15.6 respectively. I still can't import photos on my Mac to my iPhone. Your suggestions about the battery may be the solution. Currently the Maximun Battery is 84%. A new phone is not in the budget just now, and a new battery, although the cheaper alternative, would just be temporary until I can afford a new phone. Thanks for your help!