From the Washington Post:
The Senate flag, which flies atop its building when the chamber is in session, was raised around 10 a.m. Friday. But there was one problem: It was upside down. That's the universal distress symbol.
From United States Code Title 4 Chapter 1
§8. Respect for flag
No disrespect should be shown to the flag of the United States of America; the flag should not be dipped to any person or thing. Regimental colors, State flags, and organization or institutional flags are to be dipped as a mark of honor.
- The flag should never be displayed with the union down, except as a signal of dire distress in instances of extreme danger to life or property.
Just diagnosing the situation in the Senate through my TV, I'd say that sounds about right