Problem: The "upload file" link is missing.
Solution: Members of your admin user group are not authorized to upload files to the folder you are currently viewing.
Have a Site Admin access the settings for your Admin User Group.
Click the gray "Select Group Folders" button.
In the window that pops up, select the checkbox in the "R" column for the folder in question.
Select the checkbox in the "U" column as well to grant members of that admin user group privileges to upload files into all sub-folders as well.
The radio buttons in column "D" will select which folder will open by default when members of the admin user group first open File Manager.