On July 1, 2020 Khan Academy will end access to the content used by independent developers.
The Khan Desktop application uses that access to generate all of its text and video links.
The Update Tab will no longer be able to download fresh content, and the video links in the Contents Tab may or may not work in the future.
Assuming video links remain valid for a while, you can always download the videos you want for use later, creating a sort of June 2020 copy of the KA video content.
The latest version of the Contents is available by installing the .kdc file(s) available from the Contents Backup Files available page.
Note there is about 30GB of video content available.
Below are some links regarding the Khan Academy API status:
Khan Academy API page
Will topictree video URL's change
Clarification question about Khan Academy API Deprecation
Will Khan Academy Api totally be removed?