With the launch of Diablo 4 Patch 1.4.1, players have discovered that Masterworking is unavailable – but Blizzard is working on a fix for this bug.
Normally, Masterworking is accessed via the Blacksmith once it has been unlocked – otherwise, the tab is greyed out. Now, even players who have unlocked Masterworking this Season find themselves unable to tweak their gear as they could yesterday.
Thankfully, Blizzard seems to already be on the case.