My iPhone pops up a blank screen when I try to sign into an app.

I have downloaded a bunch of apps on this phone with no problem. I've also downloaded the app in questiion on my iPad with no problem.

When I go to sign into the app (it is for a security system) I get this window:

I can not go any further than this. It is supposed to be the log-in window. When I touch and hold the screen, I get a highlighted area. I've actually shared that highlighted area to Chrome and I got a "Oops" message from the app itself.

How can I defeat this pop-up window? No other app has done this.