Cannot Erase iPhone from Find my iPhone App

I have a Apple Family Plan for sharing also I’m is the plan Organizer. I try to Erase my iPhone device on Find my iPhone app and using my Family member iPhone Device.

Since my Family Member in use her Apple ID, so her is the Family Plan Adult user. Also in her iPhone Device on Find my iPhone App can locate my own Apple device.

I understand on Find my iPhone App and erase device it should be input the Pending erase device my Apple ID & Password. On my Family member “Find my iPhone” app to popup my Apple ID account and request input my Apple ID “Password”. Success apply the password, after and in Family member iPhone Find my iPhone App can see the device iPhone is “Erase Pending”

I waiting over hour ago, the pending erase iPhone device still can not erase. After in my Family member iPhone the “Find my iPhone” App to cancel the request. But I use another iPhone, also the device under my Apple ID.

After in my Account “Find my iPhone” iPhone app to Erase the device, the device Erase is immediately to take a action.

FYI, I have 3 set Apple iPhone device.

1. Need Erase Device: iPhone 7, iOS: 13.4.1
2. Family member Device: iPhone 7 Plus, iOS: 13.4.1
3. My iPhone Device: iPhone 11 Pro Max, iOS: 13.4.1

Point 1,3 - iPhone Device is using my Apple ID.

Point 2 - iPhone Device using another Apple ID, the ID under my Family Plan share member.