No, an internet connection is required to use UVI Portal in order to manage your UVI products.
You can temporarily connect your computer to the internet so that you can use UVI Portal to download, install, authorize and update your products. Once done, you can disconnect your computer from the internet.
If you want to keep this machine offline, you can still download your UVI products from another computer connected to the internet via the My Products page. Then you can transfer your downloads to your offline machine via an external storage device.
Note that an internet connection is required to activate UVI licenses directly to a computer via iLok License Manager, so this means that the use of an iLok dongle to handle your licenses is required to authorize an offline machine.
Please read the following article for more information: Installing your products via uvi.net/my-products.