NASA's final major test for its mega moon rocket and Orion spacecraft was called off due to a tech issue on Monday, the agency said on Tuesday.

During the approximate two-day test, known as a wet dress rehearsal, the launch team ran through operations to load propellant into the mega rocket's tanks, conduct a full launch countdown, demonstrate the ability to recycle the countdown clock, and also drain propellants to give them an opportunity to practice the timelines and procedures they will use for launch, according to NASA.

NASA encountered an issue Monday, with a panel on the mobile launcher that controls the core stage vent valve. The purpose of the valve is to relieve pressure from the rocket's core stage during tanking, according to NASA.

NASA's launch director made the call to stop the test for the day, given the time to resolve the issue as teams were nearing the end of their shifts. The countdown ended after partially loading liquid oxygen into the rocket's core stage tank, NASA said.

The wet dress rehearsal is the last major test before NASA's uncrewed Artemis 1 lunar mission.

After the rehearsal, NASA will review data from the test before setting a specific target launch date for the Artemis 1 launch.

Through Artemis missions, NASA will land the first woman and the first person of color on the Moon, paving the way for a long-term lunar presence and serving as a stepping stone on the way to Mars.

Read More: NASA begins critical final test on mega moon rocket