Destiny 2 players are suffering from a transmog issue where they can't unlock new looks but thankfully, you don't need to wait for an official fix to get around it.
Transmog in Destiny 2 already has annoying limitations and if you were to try to unlock a new piece of armour as an ornament during Season of the Haunted, you would run into a glitch that wouldn't let you do it.
Thankfully, the workaround for it is very easy.
In normal circumstances, you would go to the Appearance menu, click on the piece of armour you want to convert to ornament and then hold a button until that blue line fills up and unlocks it. When the glitch is present, it doesn't unlock.
To fix this, you simply need to keep holding the button even after the blue line fills up. It might take you up to 15 seconds of holding down but the ornament will unlock.
When you do get the unlock, the game might still not show your armour piece's new appearance. In order to change it to the newly unlocked ornament, you will just need to apply it once again after it got unlocked. Think of it as a manual change, rather than an automatic one.
Bungie has confirmed the existence of the bug and a patch to properly fix it is coming but until then, you will be able to properly get new looks without having to wait.