Files not accessible in Lightning

When a user uploads a file in Lightning Experience, the upload progress bar completes, but the Done button does not turn blue. After closing the upload pop up, the file does not appear to be uploaded. However, upon refreshing the page, the file becomes visible.
Despite being visible after refresh:

• The file cannot be accessed in Lightning
• Users encounter the error:
   “You do not have the level of access necessary to perform the operation you requested. Please contact the owner of the record or your administrator if access is necessary.”
• The same file is accessible in Salesforce Classic

What’s Happening:

When a file is uploaded in Salesforce, the following records are created:

• ContentDocument – Represents the file
• ContentVersion – Stores the actual file data
• ContentDocumentLink – Controls file sharing and access

In this scenario:

• The ContentDocument and ContentVersion are created successfully
• However, the ContentDocumentLink is NOT created

Why this matters:

• Lightning Experience strictly enforces sharing via ContentDocumentLink
• Without this link, Lightning users cannot access the file

Salesforce Classic is more permissive and may still display the file to admins or file owners
As a result:

• The file appears uploaded
• But is inaccessible in Lightning due to missing sharing metadata

This issue occurs when both of the following conditions are met:

Files → General Settings > “Enable Files to be ingested into Data Cloud” is enabled

The affected user has the App Permission: “Query Non-Vetoed Files” Assigned via Profile or Permission Set. This permission is intended only for Data Cloud integration users.

When assigned to a standard user, it interferes with the normal file upload process and prevents the ContentDocumentLink from being created.