These characters are added in Unicode standard version 8.0, and this app supports up to 11.0.

In this case, version 7.0 or earlier may be chosen.
You can choose an Unicode standard version from the setting screen, which can be open by a top-right tool button.

Please try it!

Yes it is right, but I think my phone can't show all the unicode characters. Help me, please, what can I do to make seeable these characters on an android 7.1.1 mobile? Thanks a lot, Gza

You need to install a font (or several fonts) that includes the Old Hungarian character block (tutorial here: www.techrepublic.com/article/Fhow-to-install-new-fonts-on-the-android-platform), then reboot your Android device and open up UnicodePad.

Or try installing the Noto fonts by Google - there's such an option in the Settings of UnicodePad (they take up quite a lot of space).

This site demonstrates and allows you to download a font with the script included: https://oldhungarian.eu

The app is functioning properly and this issue should be closed.

There's a proposal to solve this better in #154.

I see that my comment was downvoted. But it's just how it is. Android doesn't contain any font by default that shows Old Hungarian. You have to download one yourself.

Now, the suggested feature above would be, if I understood it correctly, to choose a font specifically for the block for Old Hungarian independent of what font all other characters are shown in.

But for now, you can at least show the characters by downloading the font. If you want the feature suggested in the comment above, my argument still stands that this one should be closed since the issue covered is out of scope of this app. Instead the one above is more relevant.