Thanks for the additional details. I just upgraded to 11.4.1 and tested against my Blue Iris instance and I am unable to reproduce.
I normally just use the format: http://{blue.iris.ip}:{port}/mjpg/{short_name}, but I tried your version with the trailing /video.mjpg and it worked too.
Do you have authentication required on your Blue Iris server? If I remember correctly, it’s in Blue Iris settings under Web Server → Advanced section → Authentication. I have mine set to something like "Non-LAN only" which means that I can hit the streams locally without providing any username/password, but if I try to hit it from outside my network, I have to provide the password.
Edit: Have you tried hitting the MJPG URL directly in your iPad browser (eg. outside of SharpTools.io)? If so, what are the results?