@Carlos A. Jorge - from the clear channel page, the code for POSTMAN is something similar to the above, but the CURL is a little more complex. I entered their example into POSTMAN (do you have this app?) and then converted to CURL to get the following
curl --location --request DELETE 'https://api.thingspeak.com/channels/<channelID>/feeds.json' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'api_key=1234567890'
What happens if you try the above?
