Can't download program into iPad

Some of my students have tried to download the program written in Appinventor website into iPad through scanning the QR Code. After scanning, nothing happens and can't load the program into iPad. They have tried many times but never succeed. One of my student uses iPad 9.

Many Thanks!

iOS can install apk?

Since we use App Inventor Companion to load apk to iPad, some of my students can load but some can't. Isn't my students have to jail break the iPad or do anything?

Thanks!

What are we talking about here? Is it about installing a compiled app (IPA or APK) or using AI2 with Companion on an iPad? In the latter case, Companion version 2.64.6 (build 1) is required.

Yes, we are using Companion version 2.64.6 (build 1) .