NASA's project to get humans back onto the moon and, eventually, to Mars has suffered a new blow with the postponement of a critical test.
The Artemis project has already suffered numerous delays and setbacks thanks to legal battles, the COVID-19 pandemic and issues with creating new spacesuits.
The 'wet dress rehearsal', scheduled to last for three days, included the team pumping more than 3.2 million litres of cold propellant into the tanks but that was called off for safety reasons.
"Teams have decided to scrub tanking operations for the wet dress rehearsal due to loss of ability to pressurise the mobile launcher," NASA said.
"The fans are needed to provide positive pressure to the enclosed areas within the mobile launcher and keep out hazardous gases.
"Technicians are unable to safely proceed with loading the propellants into the rocket's core stage and interim cryogenic propulsion stage without this capability."
The space agency is hoping to resume testing on April 4, local time, however that depends on several factors.
Mike Sarafin, Artemis I mission manager and Charlie Blackwell-Thompson, Artemis launch directors said their teams were still troubleshooting the issue with hope it could be resolved overnight.
Favourable weather conditions will also be needed to resume the testing. On Saturday four lightning strikes were detected near the rocket.
The launchpad's lightning protection system - three towers that help redirect current into the ground - diverted the strikes.
The dress rehearsal - a test launch countdown - was occurring at Florida's Kennedy Space Centre as a "big milestone" ahead of the first Artemis launch.
The Space Launch System megarocket and the Orion crew capsule had been rolled out to Launch Pad 39B ahead of the 45-hour, 40 minute countdown clock starting with most of the prelaunch procedures walked through, without a launch actually occurring.
The count gets all the way down to 33 seconds before it is stopped. It's then reset to 10 minutes and the final steps run through again before then stopping 10 seconds before take off.
Other checks during the rehearsal included closing the crew module hatch and conducting leak tests. The team also fills the sound suppression system with water at the launch pad.
It is used to "dampen and absorb acoustic energy during liftoff", NASA said.
"Even though the Space Launch System engines will not fire during this test, teams are practising carrying out operations as they would on launch day."