How to reset a parent-managed kid's phone?

My daughter has changed her lock screen password. Didn't write it down. And had forgotten it. And so her phone is locked. What I observe is: * After restart, she's been asked a code. I can't find anyway to reset that code. * Her phone is connected to the web. I can see today's date on the Family Link page for her account. * I cannot find a way to switch from user on her phone (i.e. logging with my own account) * Stopping and Restarting the device is not possible. The phone remains on that lock screen. Only a hard-shutdown is possible (Volume up/Volume down/Power during a few seconds). * The phone doesn't ring when I ask it to ring from the Family Link page. I tried various ways to connect to the phone : * The procedures with *Find My Device* don't work, because : * When I connect to Google with my own account, I cannot switch to her account, and hence don't see her phone as candidate phone to work on. * When I connect with her account, she has no rights to use that application. * The Family Link page provides a 6-digits code that changes every hour supposedly providing access to the phone. It doesn't. The phone keeps saying invalid password. * The Family Link page lets define a new lock screen password. Defining a new password doesn't help despite a hard restart of the phone. What are my options now ? A hard reset of the phone is acceptable. But even that I don't succeed to do. ---- PS: The phone is a Samsung A03