Smush request timed out

Hi!

When I try to bulk smush my images, I always get this error:

Smush request timed out, You can try setting a higher value for WP_SMUSH_API_TIMEOUT.
Error posting to API: cURL error 6: Couldn't resolve host 'smushpro.wpmudev.org'

How can we fix that?

Thank you!

Jan