If you import photos from a camera without GPS signal your photos don't have locations in their metadata. Therefore the app is not able to detect the locations and add them. You can check the manual of your external camera to find out, if it supports GPS or not.
The same issue could appear when you didn't allow your smartphone camera to access your location. This is managed inside Settings:
On iOS: Settings > Privacy > Location Services > Camera > When Use
On Android: (different on all devices) Camera Setting > Location Tags > On
If you create a moment and want to add the current location please check if you have allowed Journi to access your location:
On iOS: Go to Settings > Search for "Journi" > enable "Location" to "While Using"
On Android: Go to Settings > Apps or Application Manager > Journi > Permissions and enable Location.