Hello,
I did some research on this topic, Microsoft announced that Virtual network TAP Preview is currently on hold in all Azure regions, but you can send them an email to "azurevnettap@microsoft.com" with your subscription ID and they will notify you with future updates about the preview.
They offered another alternatives using the "Packet Broker partner solutions" with Virtual network TAP partner solutions
such as:
Gigamon GigaSECURE
Ixia CloudLens
Nubeva Prisms
Big Switch Big Monitoring Fabric
Please click on Accepted Answer if this answer help you.