Unable to add devices to "find my iPhone" app
After an update to IOS 13 the "find my iPhone" app only shows my iPhone. There is no option to add a device (that I can find). Before updating to the new IOS I had my aging parents iPhones listed on the app so that I could locate them if something should happen, but now they are missing. I confirmed that they have their "find my iPhone 'on'", they have IOS 13.1.3 and they are signed into their Apple ID.
iPhone XS, iOS 13