I use Lr Classic and Mobile and my mobile images used to sync automatically and show up in the proper destination within Classic. Recently, the images stopped showing altogether. I did get a new phone but downloaded the Lr Mobile app. Why is this happening?
For this to work, both your phone and your Mac need to be logged onto the same creative cloud account. Are you logged on to the same account on both? Also, check if the images you shoot with your phone show up in https://lightroom.adobe.com. Make sure sync (the little cloud icon on either) is turned on and not paused. Lastly, check what the settings are for where to sync to in Classic in Preferences->Lightroom Sync. There is a place there where you specify where cloud images are synced to on your local machine.