Box toolkit authentication issue in salesforce while creating files from attachment

I have a requirement where, once an object is updated from an external system, a process is triggered that will fetch all the files from the updated object and save the files into a specified box folder into another object that is newly created.
I have used the Box toolkit method - createFileFromAttachment() to add the files to the new folder.
The method is also getting executed in the future context and callouts are allowed. Yet the process throws an authentication error that starts with:

"boxtoolkitToolkit:[AUTH_WRAPPER_PREPARE_FAIL_MESSAGE=Unable to use default credentials to make a callout to Box (maybe this is in a trigger, constructor, or after a DML statement):, authWrapper=BoxAuthWrapper:[adminSettings=box__BoxUser_Settings__c:{}, "

Once the process gets executed, if multiple files need to be transferred, only one file gets transferred to the destination folder, and the other files are stopped after the same error is encountered.

I’m implementing the requirement in Salesforce using Apex.

Your collective efforts and willingness to help are truly appreciated.
Thank You
Best Regards