For export to be available,
- Your organisation have a 3D Export licence and export credits are still available for your license.
- You need to have 3D export permissions, which your account administrator can provide you.
Check with your Nearmap account administrator that they have granted you the correct licence and permissions for 3D Export. It is possible that if you do have a 3D Export licence, it is on a separate licence. If your administrator needs to change the licence, they can use these instructions: Manage a User's Licence.