On my wife's LG G5 she uses Google Photos as her choice of photo gallery app. She took photos until her device memory filled up, so I bought her a micro-SD card. I went into File Manager and moved all the photos from internal memory to the SD card, then set the camera app to store new photos on the SD card as the default location.
Now when I open the Google Photos app it doesn't show any of the old photos. It shows new photos taken since the SD card was installed, but not the old ones. If I look in the Gallery app I can see all the photos on the SD card, both old and new.
I suspect the same issue would occur if I wanted to side load photos taken with another camera onto the SD card.
How can I make the Google Photos app library find the old files in the new location? Or in other words, rebuild the index of photos, or clear the cache, or whatever I need to do so the app will start looking at the contents of the SD card?