Cannot Use Lunarwing Form

With the Shadowlands pre-patch, the Archdruid's Lunarwing Form is a character customization option that you select at the Barber Shop.

You can only select this customization if you meet the following conditions: 

• Your character must have the Expert Riding skill
• Your character must not have the flight form glyphed
• You must have completed the quest You can't take the sky from me with one character on your Battle.net account

Note: If the druid character that completed the quest line to unlock the Lunarwing Form was transferred from a different Battle.net  account, it won't unlock this feature for other druids on the current account. This is intended, and you would need to complete the quest line with a character in this Battle.net account.