Bobby....
You sir....are a genius.
This Photos syncing over cellular has been one of the most frustrating issues with Apple OS updates breaking EVERYTHING unnecessarily.
Your workaround is amazing. Works perfectly.
I felt bad for the original poster getting lousy support from these people on this thread. English isn't even his first language but I understood very clearly exactly what he was saying.
The Photos app on his laptop stopped syncing over cellular (using a mobile device as a hotspot to share cellular data to your computer) with the High Sierra OS update. It worked with Sierra and stopped working with High Sierra....not Photos for iOS on his iPhone....Photos for mac, just as he said. Can't roll my eyes hard enough. Stupid clear.
So, for anyone else who wants your Photos app to again sync over cellular data shared from a mobile device's hotspot. Follow these steps (thank you, Bobby):
1. You need two apple computers. I used two apple laptops, a MacBook Air and a MacBook Pro.
2. Your primary computer is the computer with your active Photos library on it that you wish to use over cellular data shared from your mobile device's hotspot. Your secondary computer will be the computer that will provide a Wi-Fi connection to your primary computer.
3. Connect your mobile device with Personal Hotspot enabled to your secondary computer, preferably using a USB cable for the best, fastest, most reliable connection.
4. Launch System Preferences on your secondary computer, click "Network." Disable Wi-Fi and verify that there is a green dot next to iPhone USB and you see "Status: Connected"
5. If you don't see iPhone USB with a green dot next to it, check your mobile device. Unlock it and click "Trust" when prompted. iPhone USB should now show up in your Network settings.
6. Click the back arrow in the upper left of System Preferences and then click "Sharing"
Here is the happy part....
7. Click Internet Sharing in the Service list on the left.
8. Select "iPhone USB" in the "Share your connection from:" drop-down menu.
9. Click the checkmark box next to Wi-Fi in the "To computers using:" section below the previously mentioned drop-down menu.
10. Click Wi-Fi Options and configure the Wi-Fi name, security, and password.
11. After you save those Wi-Fi settings, click the checkmark box next to "Internet Sharing" in the Service list on the left.
12. On your primary computer, enable Wi-Fi and look for the Wi-Fi network name (SSID) that you created on your secondary computer. Join it with the password you created.
********
- Nick
******
[Edited by Host]