Account suddenly says I don't own Minecraft

Account suddenly says I don't own Minecraft and refuses to let me login. When logging in on the website it doesn't show that I own the game either. No idea what could have caused it as I played perfectly fine up to this morning. I've had the game for so long I no longer have my receipt for it and no idea how to go about proving I own it. The only thing I can think is that it has something to do with the microsoft integration