Hello Quach Son,
To start us off, this article explains how to use this feature and make sure it is turned on as expected: Share your location in Find My on iPhone. Your options for sharing in specific circumstances are explained in detail here: Find people and share your location with Find My.
If the issue persists after confirming that you have everything set up properly as explained in the previous articles, try taking the following steps which may help with this: restart your iPhone, make sure it is up to date, close the Find My app then reopen it.
Restart your iPhone
"Press and hold either volume button and the side button until the power-off slider appears.
Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."
Update your iPhone or iPad
"Back up your device using iCloud or your computer.
Plug your device into power and connect to the internet with Wi-Fi.
Go to Settings > General, then tap Software Update.
If you see more than one software update option available, choose the one that you want to install.
Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now."
Close an app on your iPhone or iPod touch
"From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
Swipe right or left to find the app that you want to close.
Swipe up on the app's preview to close the app."
Let us know if we can help with anything else at all. Take care.
