Hmm…
Two things. First, check that you don’t have any spaces before or after the API key (the next version will remove them automatically, but the current version doesn’t).
If that still doesn’t work, you can check your API key with World Weather Online at: https://developer.worldweatheronline.com/io-docs
From the drop-down box, select “Free Weather API”, then put in your API key. Next, click on the “Get Local Weather” (first option) to expand it. Leave all the values as they are and click “try it”. This submits a request for weather data using your key. It will then show you the result just below. If you see results like “403 Forbidden” and “Developer Inactive”, this indicates that there is a problem with the API key. In that case you may need to register again to get a new API key.
Sorry, it’s a bit of a hassle with the whole API key thing. I’m looking to move to a key-less setup in the near(ish) future which should avoid all this.
Dan