New iPhone SE (2nd Gen) won't upload pictures to my MacBook Air 2017 (Mohave)

Have you tried this process given below? Transfer photos and videos from your iPhone, iPad, or iPod ...

Extracted from the above link....

"Import to your Mac

You can use the Photos app to import photos from your iPhone, iPad, or iPod touch to your Mac.

1. Connect your iPhone, iPad, or iPod touch to your Mac with a USB cable.
2. Open the Photos app on your computer.
3. The Photos app shows an Import screen with all the photos and videos that are on your connected device. If the Import screen doesn't automatically appear, click the device's name in the Photos sidebar.
4. If asked, unlock your iOS or iPadOS device using your passcode. If you see a prompt on your iOS or iPadOS device asking you to Trust This Computer, tap Trust to continue.
5. Choose where you want to import your photos. Next to "Import to," you can choose an existing album or create a new one.
6. Select the photos you want to import and click Import Selected, or click Import All New Photos.
7. 
8. Wait for the process to finish, then disconnect your device from your Mac.

Learn what to do if you can't import photos from your iPhone, iPad, or iPod touch to your computer."

Important: If you already use iCloud Photos on your Mac and devices, your photos are updated automatically. You can’t use the syncing method described here unless you turn off iCloud Photos in Photos preferences. 

See the pic below which is self-explanatory