You may get the error 401 in the following cases:

• You did not specify your API key in the API request.
• Your API key is not activated yet. Within the next couple of hours, it will be activated and ready to use.
• You are using the wrong API key in the API request. Please check the right API key in your personal account.
• You are using a Free subscription and try requesting data available in other subscriptions. For example, 16 days/daily forecast API, historical weather data, Weather maps 2.0, etc). Please, check your subscription in your personal account.