Larry,
Based upon your description, I believe that particular tablet does not allow third party apps to access the external SD card at all. You said you spoke with the manufacturer, but they obviously didn't know what they were talking about. You can go back to them now (if you want) and explain that no app on your tablet has access to the external SD card, so this must be a configuration issue on their end. They most likely have not set up the permissions for the external SD card correctly. This is not the first time I've seen this unfortunately - some of the off-brand tablets seem to experience this problem due to the manufacturers not setting up the OS correctly.
It might still be a good idea to see if an app like ES File Explorer can access the external SD card. If not, then I am confident in what I stated above.
Mike
Based upon your description, I believe that particular tablet does not allow third party apps to access the external SD card at all. You said you spoke with the manufacturer, but they obviously didn't know what they were talking about. You can go back to them now (if you want) and explain that no app on your tablet has access to the external SD card, so this must be a configuration issue on their end. They most likely have not set up the permissions for the external SD card correctly. This is not the first time I've seen this unfortunately - some of the off-brand tablets seem to experience this problem due to the manufacturers not setting up the OS correctly.
It might still be a good idea to see if an app like ES File Explorer can access the external SD card. If not, then I am confident in what I stated above.
Mike