Solution
This behavior can occur if you are opening NI Package Manager (NIPM) on a PC that has Ethernet connectivity to a network, but does not have access to the internet. See Additional Information below for the cause of this behavior.
To improve the behavior of NIPM on computers without internet access, you can either disconnect the computer from the WIFI or Ethernet network completely before opening NI Package Manager or perform the following steps:
1. Open an command prompt with administrator privileges to C:\Program Files\National Instruments\NI Package Manager.
2. Run the command:
nipkg remove ni-package-manager-released-feed --force-essential
3. Open NI Package Manager.
4. Click settings button (
) and uncheck the options In the NIPM settings window, uncheck the options Show the BROWSE PRODUCTS tab and auto-register product feeds and Automatically download and install missing dependencies from NI.com.

Please note that if you upgrade NI Package Manager in the future, you will need to repeat these steps.