Solution
When installing new NI software, users are given a choice to evaluate it and its add-ons for a set number of days before being asked to purchase it. However, if the evaluated software add-on edition or version installed on the machine doesn't match the one that was purchased, the activation will not work. To solve this, the add-on has to be removed through NI Package Manager and installed again by selecting and activating the correct version, as shown below:
1. Open the NI Package Manager and select Installed tab at the top

2. Type the name of the affected package into the search bar at the top right corner. In the image below
Sound and Vibration Toolkit is used as an example

3. Select the appropriate item and click Remove

4. Once the package is uninstalled, install the add-on again and type in your serial number to activate the Base version.