Hi ba365guy,
My marketing server version is 9.1.0000.14430, and enabled with 2020 wave 1 early access.
What's more, my application has been updated several days ago,

I found that email designer has changed to new design UI:

Below is my test, my test recipients can see their QR code.
1. Event registration records have been created for corresponding contacts.

2. A simple customer journey.

3. Email with QR Code

Event registration ID in QR Code in delivered email can match to ID in event registration record.
So I suggest you could check whether there is update for your marketing application, and update the application to latest version to test again.
Regards,
Clofly