I have set up Box Sign in our Salesforce org and created a Box Sign button on the opportunity object. The design is to select from a set of templates and then the process pulls in 1 or 2 contacts from the opportunity as signers and then the user can send the Box Sign from there.

When running this as the admin, it works seamlessly. I can click "Preview and Send" to preview the document and then send from there. When I send, it immediately triggers the email to the client to sign and a BoxSign record is created in the BoxSigns related list on the opportunity.

When my non-admin users run this, if they click "Preview and Send" the preview never loads and instead a "Box Sign is queued successfully" green toast message displays OR sometimes it tries to load the preview page, but then throws an invalid link error. The biggest issue is that when the non-admins select either "Send" or "Preview & Send", the BoxSign record is never created in Salesforce.