It may happen that when you first try to send an SMS you get the error message:

“No response. Maybe there is a problem with your internet connection.”

The most likely reason is that some utility program, like Little Snitch or Internet Cleanup, prevents the SMS Mac software to make a connection to the Internet. Please configure these programs to allow SMS Mac to make an Internet connection.

Another reason might be that the SMS Mac server is too busy. Your SMS is likely still submitted correctly. You can use the Email a copy of the SMS option to check this. Check your email for a message from SMS Mac that your message has been submitted. You can find the option Email a copy of the SMS in the Handle Reports preference pane.