An upcoming security update for Google Drive will increase the security of your shared documents but likely break many shared links. Google is rolling out the update over the next few months in three phases to give Google Workspace admins enough time to prepare. The update will be rolling out on September 13th, 2021, to make file sharing more secure. If you wish to continue sharing your Google Drive documents, you will need to update your posts with the new links that contain the new resource key. Google Drive security update will cause any Google Drive links that you previously shared on websites, social media, or elsewhere to no longer work.
Source: https://www.bleepingcomputer.com/news/google/a-google-drive-security-update-will-break-some-of-your-shared-links/