Hi all,
I can confirm that you MUST connect your Zwift account to your Garmin Connect account to unlock the jersey to have the Garmin Kit appear in your garage. I just connect Zwift to my Garmin Connect account, then logged into Zwift and the Kit was in my Zwift garage.
The easiest way to do this is - log into your Zwift account on your computer, click the menu icon(the 3 horizontal lines on the top right hand corner), click your your icon(image), then select Connections. Search for Garmin then click connect. You must have a Garmin Connecct Account for this to work and complete at least one Garmin ride.
Log back into Zwift and your Garim kit should be in your Zwift garage.
Cheers