Sleep widget "No data Today"

I've setup the Sleep Widget on my iPhone, but it always displays "No data Today"

When I open the Health app, my sleep data is there (for the last night)

For example, we're August 31st and I can see the sleep data of the night of the 30th, which is normal.

But the Sleep Widget seems to think that it should display today's data (the 31st)... Weird

Any idea why this is happening?