NASA faced the same problem with its lunar rocket SLS again: during refueling, the fuel did not fill the tanks.

NASA continues preparing the lunar rocket SLS for the crewed Artemis II mission

NASA is actively working on preparing the SLS rocket, which is set to become the first flight of humans to the Moon in 50 years—Artemis II. In early February a “wet” full-scale rehearsal was scheduled, during which the rocket would be fueled with cryogenic propellant. However, a hydrogen leak through the flanges of the ground pipeline forced the test to be postponed until the fault was fixed, and the launch was moved from February to March.

Subsequent events
Date What happened 12 February At the cosmodrome the fueling check began with new seals. The first stage tank was filled with liquid hydrogen. No leaks were detected, but fuel is being fed into the rocket slowly and with difficulty. Analysis showed that the problem is most likely in the ground pumping equipment. Saturday–Sunday Engineers cleaned the pipelines and checked auxiliary equipment. A hydrogen feed filter replacement is planned— it is considered the main cause of delays.

After repairs a new analysis of the situation and a date for another “wet” rehearsal, expected at the end of February, are planned. Thus, March remains the earliest possible launch window for the Artemis II mission.