Pressurization issue has been detected. Teams are working the issue and continuing prop load.

If this can't be solved, this will become a WDR (Wet Dress Rehearsal) test.

‍A pressurant valve appears to be frozen, so unless it starts operating soon, no launch today
Source: @elonmusk

‍Learned a lot today, now offloading propellant, retrying in a few days …
Source: @elonmusk

Editor's notes:
• Due to the propellants needed to refill the tank farms, the launch is expected 2-3 days from now.
• 150 tankers are expected.
• Launch attempt is now NET Wednesday Apr 19.
• Coverage will still be provided.

Teams are working towards Thursday, April 20 for the first flight test of a fully integrated Starship and Super Heavy rocket → http://spacex.com/launches/mission/?missionId=starship-flight-test
Source: @SpaceX

Targeting Wednesday, April 19 for Falcon 9’s launch of 21 second-generation Starlink satellites to low-Earth orbit from SLC-40 in Florida → http://spacex.com/launches
Source: @SpaceX

[Launch is reportedly no longer happening on Apr 20. Next opportunity is Apr 21 but there is no official confirmation of the change or next target. However, the flight restriction for Thursday has been lifted.]

April 20 is definitely out for the Starship flight test, per two sources. No confirmation on whether it slips just a day or further. For more details I will refer you to SpaceX’s social channels.
Source: @SciGuySpace

UPDATE

As per the FAA's advisory, SpaceX is now targeting:
Friday Apr 21: 12:00 → 15:05 UTC

The backup windows are:
Apr 23-28: 12:00 → 15:05 UTC

A Temporary Flight Restriction has been reissued by the FAA for Thu Apr 20. Awaiting clarification from SpaceX.

As per the latest FAA's advisory, SpaceX's Starship is now targeting:
Thu. Apr 20: 13:28 → 15:05 UTC

The backup windows are:
Apr 21: 12:00 → 15:05 UTC
Apr 23-28: 12:00 → 15:05 UTC

Now targeting 14:31 UTC for today's launch of Starlink, all systems still looking good
Source: @SpaceX

🚀 Next launch Starlink Group 6-2
Rocket Falcon 9 Block 5
From SLC-40, Cape Canaveral 🇺🇸

🕙 Launch time
April 19th, 14:31 UTC

🌍 Mission information
Type Communications
Orbit Low Earth Orbit

🚀 Vehicle information
Core B1073.8 (8th flight ♻️)
Landing ASOG (ASDS 🌊)

ℹ️ A batch of 21 v2 satellites for the Starlink mega-constellation - SpaceX's project for space-based Internet communication system.
#Launch

Liftoff!
Source: @SpaceX

Falcon 9’s first stage has landed on the A Shortfall of Gravitas droneship
Source: @SpaceX

Deployment of 21 Starlink satellites confirmed
Source: @SpaceX

Teams continue working towards Thursday, April 20 for the first flight test of a fully integrated Starship and Super Heavy rocket → https://www.youtube.com/live/-1wcilQ58hI
Source: @SpaceX