Text Me The App gives 404 File not found error

We are using the Text me The App Feature and integrated it into our own Website.
But when we send the Phone Number we get a File Not Found here: http://ift.tt/2vSv1gH

We use the following Link from a desktop: http://ift.tt/2x66Eup

It should all be setup as descibed inthe Documentation. Any Idea? Thanks