All my lists disappeared

I have been using the Microsoft To Do App on my Android phone for a long time. It is also on my Windows PC (although I seldom use it there). Today I got a message from Microsoft on my phone request me to Sync (I can't remember exactly what the message said), but I did it. Now all my lists and tasks have disappeared. When I Google the issue, I am directed to Outlook deleted folder, but this was not an Outlook related app. I've signed in on the Web and it is also blank. Is there a way I can find and restore my lists? (One of the lists was shared with my partner).