Adding Fabric Groups might not show any compute resources. It can take an hour (Default) for the inventory to refresh.
To speed things up you can refresh the inventory manually. You may have to do the same when adding new portgroups for example, and you want to use them in vCAC etc.
Browse to Infrastructure > Compute Resources > Compute Resources
Click your Compute Resource and select Data Collection
In the Inventory Section – click Request Now
Then give it a minute
Status should then change to Succeeded
That’s it. You should now see the inventory when adding Fabric Groups / additional resources etc.