NitroPhone: Google Play Services in Sandbox not starting. Does anyone have the same problem?

Dear friends,

I hope this finds you all well. I have followed the installation of Google Play Services instructions to the letter with painstaking accuracy several times using the Split Installer. Google Play Services is installed. However, when launching the app, the app does not launch at all (save for the first google logo and then freezes).

https://docs.nitrokey.com/nitrophone/apps.html

Grateful to learn whether anyone has encountered the same problem and / or what the fix could be.

I look forward to hearing from someone kind enough to share his knowledge with me.

Thank you.

MT