WhatsApp Windows app: No way to sync to phone, no way to backup chats

Windows 11 v. 25H2

When I installed the Windows WhatsApp app, I linked it to my phone. 99% of my messages are on the Microsoft App, not on my phone. There seems to be no way to link them, or to backup. The two devices are not connected, and there is no way to sync them. According to AI, they are likely running separately, on separate programs --- one on the phone, and one on the Windows App

None of my backups are saved anywhere on Windows.  AI had me look in several places, and they just aren't there. There seems to now be no way to update the app or backup what is there without forwarding it chat by chat to myself, but even then, it can't be restored.  Is there something AI missed? Is there any way to fix this without losing all of my chats?

My son lives in Europe and all of our chats are on the Windows WhatsApp app.