What is the status code you get from ThingSpeak when you update your channel? If you are using the Write Data API and get a HTTP 200 response code with a number representing an entry_id, then your data was accepted by ThingSpeak.
With a free license of ThingSpeak you can only update the channel every 15s. Any more frequent updates are rejected with a HTTP 200 status code and "0" response.
If you want to update your channel every 5s, consider purchasing a ThingSpeak license.
