Sometimes it so happens that a user cannot view the values of a managed metadata column, even if the user has been granted permissions to the library or file. This simply means that the user is still missing permissions, how strange this may sound. The cause? SharePoint operates with a hidden list in which it stores all metadata for the impacted sitecollection. And as it may turn out, your user doesn’t have access to it!
To check the permissions of this hidden list, named TaxonomyHiddenList, you can go to:
In case the user does not have the correct permissions, either grant the user reading permissions to this list or grant all users reading permissions to this list, for example through
NT AUTHORITY\authenticated users or