At the end of 2017, Google removed Chrome App listings from their web store.
You can still find and install the WeVideo apps via a direct link:
If you need to force install the extension for your organizational unit users, you can follow the instructions on this page https://support.google.com/chrome/a/answer/6177431?hl=en . If the app does not appear in the search there, you can add a custom app and use the following ID okgjbfikepgflmlelgfgecmgjnmnmnnb and URL from above.
Please note that Chrome Apps will be reaching an end of life in the near future. You can bookmark this link for updates and more information from the Google team https://blog.chromium.org/2016/08/from-chrome-apps-to-web.html
At such a time, please continue accessing WeVideo directly from www.wevideo.com or in the mobile apps.
If you click on "Log in with Google" you will access the same account you always have been from the app. All of your content will still be on wevideo.com after the app is removed.