Check whether Visual force page access of the component has been added to the required user/profile or not. if it is added against the profile then user able to upload the files.
Issue: Community issue not able to upload files in XfilesPro BiSync component. Resolution: The community user does not have access to the Opportunity. The user is not able to query as the Sharing setting for Opportunity is Private. It is required ...
Issue: Restricting/allowing specific users from viewing MP3 and WAV files within the Xfiles component of the opportunity record. We're aware of the Xfiles Common Setting for allowing File Extensions, which enables granting access to specific users ...
For uploading the more than 190 MB of files>>> Solution: Open Xfiles Common settings and in the Select Upload Type For S3 Field add ClientId_Secret and it will work as expected,