Here's how to update ZOOM's downloaded application.
Open your downloaded Zoom app and click on the
[Sign In with SSO] link.
In the next window, make sure that the text box says union and not union.edu.
(You will not be able to change the .zoom.us in the box.)
Click on the [Continue] button in the lower right corner.
You will be taken to the College's Single Sign On page where you'll need to enter your college username (not your full email address) and password. Click on the [Sign In] button.
When the ZOOM application opens, there will be a notification at the top of the window - click on the [UPDATE] link to get started.
You could still need an update even if you're not getting the notice.
In your Zoom application window, click on your photo or icon in the upper right corner of the application window.
In the drop-down menu, select [Check for Updates].
In the Update Available window that pops up, click on the blue [Update] or [Install] button. 
The application will automatically update and then log you in again, and you will see a notice in the upper right corner that says, "Your client has been successfully updated."
Click here for a Knowledge Base article with more information about using Zoom.
If you are having difficulty or you have unanswered questions, please contact the Help Desk through the ITS Service Catalog or call (518) 388-6400.