Solution
NI software can be downloaded from two places: NI Package Manager (NIPM) and ni.com/download. For the latter, this webpage utilizes an entitlement filter to verify your entitlements and determine whether you have permission to download a given version of software. In some cases, the download button for that software will be disabled and prevent you from downloading the software.
To fix this problem and enable the download button, first, ensure that you have purchased a software license with an accompanying service program. Then, confirm that the license and program not expired. At this point, if the download button is still disabled, make sure that the appropriate serial numbers are registered in your account. To do this, refer to
Finding the Serial Number of My NI Software to help you find your serial number and
Registering Products to My NI User Account to help you register the serial number. Finally, registration takes up to 24 hours to complete, therefore, wait a day and come back to check the status of the download button.
Hopefully now the download button is enabled, and you are able to download the software, If the button is still disabled, contact NI Technical Support, and they will help you with the downloading the software.