Unable to add collaborators

Hi Zach, 

Welcome to Box Community and glad to assist! 

Try these steps and see if it would work, 

• Please ensure your web browser is the latest version of Chrome, Firefox, Safari, or Edge
• Try clearing your browser's cache. If this does not resolve your issue, please proceed to the next step.
• Verify that you are using one of our recommended operating systems.

Hope it works!