User Access Limitations on Files

Non-admin users that belong to a profile with Chatter not enabled can’t open, preview, upload, nor download Files. For example, a particular user can’t open Files even when the file sharing settings are enabled for the entire organization. 

Error messages for this scenario differ between Experience (LEX) and Salesforce Classic. For instance,

LEX: "We couldn't find the record you're trying to access. It may have been deleted by another user, or there may have been a system error. Ask your administrator for help."

Salesforce Classic: "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. For more information, see Insufficient Privileges Errors."