Hi
I suspect you are not the data owner of the property boundaries (or an Admin) in your Portal. If you want to export the boundaries as a new feature class you can ask either the data owner or your Portal Admin to:
1: Display the metadata for the item
2: Click the Settings tab
3: Ask for the "Allow others to export to different formats" tick box is ticked. It's found under the Export Data part of the form.
I hope this helps.
Thanks ed