Photos not shown in Places

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

It depends on the setting of the zoom slider, if you will see a photo thumbnail for a certain area. To see more places markers zoom in on the area where you want to see photos. If you zoom out, the some places markers will vanish and be merged into other markers close by.

Photos is not always updating the library instantly, when you import photos or assign locations to photos. Restarting Photos will force it to save all changes to the library and then the smart albums will be updated, the Places and the People.