About the Box for Salesforce toolkit

Hi there, 

Welcome to Box Community and glad to help! 

Looks like you're logged in to your individual Box account. Note that the Box for Salesforce integration is available at no extra charge for joint Box Enterprise/Salesforce customers. To get the integration, contact your Box Customer Success Manager or visit http://www.box.com/services/salesforce.

Meanwhile,  here's your complete guide to install Box for Salesforce. 

Thanks for posting! 

If you log in as another user with the same profile and run it, it will complete successfully.
If you assign the permission set "Box_App_User" to the user who is currently experiencing the error, it will complete successfully.
By the way, the error content is "Line: 79, Column: 1
System.AuraHandledException: Script-thrown exception".