The launch attempt comes one day after the Federal Aviation Administration granted SpaceX final regulatory approval for launch. 

Elon Musk tweeted, "A pressurant valve appears to be frozen, so unless it starts operating soon, no launch today." 

Recall, Musk recently gave the test launch of Starship around a 50% chance of succeeding on its first orbital flight. 

There's still no timeframe on when the next launch window will open. 

Update (0910ET):

SpaceX intends to launch its massive Starship rocket into space at approximately 0920 ET. Should everything proceed smoothly, Starship is set to become the world's most powerful rocket.

A lot is at stake for the SpaceX team. 

"We really need to fly this vehicle to understand it," Gwynne Shotwell, SpaceX's president, told reporters in February. 

Elon Musk recently gave the test launch of Starship around a 50% chance of succeeding on its first orbital flight.