Error posting to API: cURL error 6: Could not resolve host: smushpro.wpmudev.org

2 things have happened...

My plugin will not update and my website says that all the images need to be smushed, even though they have been for over a month, and when I try to re-smush I get the same error as when trying to update the plugin:

Error posting to API: cURL error 6: Could not resolve host: smushpro.wpmudev.org