I’ve been using a variant of Ryan’s script for quite some time, and since the last change to the endpoint, it has been many months without issue.
I just tested my script, and got a video from this morning. I also just checked the endpoint in my script, and it is the same as that contained in the current version of Ryan’s script, as currently seen in github. Indeed, to be sure, I just ran an unchanged version of the script on github, bar the credentials change, and it worked for me.
I wonder if it’s something to do with your location? Why don’t you change the server to the prde one, just on the off chance? Can’t hurt, for one test.
Another thought, maybe your IFTTT credentials approval hasn’t had chance to replicate around all the Blink servers yet?
Either way, the API endpoint appears to be correct still.