I actually solved this pretty easily after reading all the posts, but not exactly what was posted worked for me.

in the MMM-OpenWeatherMapForecast module director, edit the MMM-OpenWeatherMapForecast.js file.

under defaults, change

Endpoint:

From

“https://api.openweathermap.org/data/2.5/onecall”

To

“https://api.openweathermap.org/data/3.0/onecall”

then use an api key created after you subscribed, this last step may or may not be needed, but coincidentally or not, the last api key I made after making the above change was what worked.

@sdetweil I appreciate your expertise, that is what got me there, your fork is now 18 publications behind so I think the node_helper.js file that comes with the main install must look a lot different. It contains a call back to the .js file I mentioned, and does not have the url that you can edit in that file any more. Later I also discovered there is a string you can add in the config file that will change that value to 3.0 as well, unfortunate that they made 3.0 incompatible for new users with 2.5, because now the choice is to break all the old installs, or break all the new ones without chasing down this post.

I actually solved this pretty easily after reading all the posts, but not exactly what was posted worked for me.

in the MMM-OpenWeatherMapForecast module director, edit the MMM-OpenWeatherMapForecast.js file.

under defaults, change

Endpoint:

From

“https://api.openweathermap.org/data/2.5/onecall”

To

“https://api.openweathermap.org/data/3.0/onecall”

then use an api key created after you subscribed, this last step may or may not be needed, but coincidentally or not, the last api key I made after making the above change was what worked.