Excerpt from the linked content^1 by Eric Berger:

>At just over two minutes to go before SpaceX's Falcon 9 rocket was due to launch a crew of four astronauts to the International Space Station early on Monday, the mission was scrubbed due to an issue with igniter fluid.

>NASA's Crew-6 mission had been due to take off at 1:45 am ET from Launch Complex 39-A in Florida, at Kennedy Space Center.

>During the space agency's webcast, the host first mentioned the issue with the TEA-TEB igniter fluid about five minutes before the anticipated liftoff time. Mission operators were not able to clear the technical issue before the instantaneous launch window opened.

>The crew was safe on board the Crew Dragon spacecraft.

>NASA astronauts Stephen Bowen, the mission commander, and Warren “Woody” Hoburg, its pilot, along with United Arab Emirates astronaut Sultan Alneyadi and Roscosmos cosmonaut Andrey Fedyaev, both mission specialists, will egress the vehicle later on Monday morning after propellant is off-loaded from the rocket.

> 

>Shortly after the scrub, SpaceX tweeted a little bit more information about the cause: "Standing down from tonight's launch of Crew-6 due to a TEA-TEB ground system issue," the company said.

>TEA-TEB is a combination of triethylaluminum (TEA) and triethylborane (TEB). Essentially, these are two different metal elements each linked to three hydrocarbon atoms.

>These molecules are held together by rather tenuous bonds that break easily. When it comes into contact with oxygen, therefore, TEA-TEB spontaneously combusts.

>Given the danger involved in working with the chemical, SpaceX probably made a good decision to stand down Monday morning's launch.

^1 Eric Berger for Condé Nast’s Ars Technica, 27 Feb. 2023 07:15 UTC, https://arstechnica.com/science/2023/02/spacex-scrubs-crew-6-launch-due-to-an-issue-with-its-igniter-fluid/