Sorry, the link has a typo - the channel ID was missing. In the below link, replace the channel ID 12397 with your channel ID:
https://thingspeak.com/channels/12397/private_show
In the private view of your channel, do you see data in your channels? If you do see data, then another way to download data from the channel is the following url (note that you need to change the channelID 12397 to your channel ID):
https://thingspeak.com/channels/12397/feeds.csv?
This will download a csv with 100 rows in it. You can change this by using the info on this link:
https://www.mathworks.com/help/thingspeak/get-a-channel-feed.html
On clicking on the button to "Download all of this Channel's feeds in CSV format" in the "Data Import/Export" tab of a private channel I am able to download data. Are you able to download your data now?
-Adarsh