OpenVPN Connection and Cannot resolve host address

Hi,
I try to establish an OpenVPN connection from smartphone to IPFire.
I have set up a service of desec.io under Dienst/Dynamisches DNS/Hinzufügen.
The hostname xxxx.dedyn.io is displayed green. The assigned IP from the provider is
identical to the updated IP at desec.io.

When building an OpenVPN connection with OpenVPN for Android, I get the error:
Cannot resolve host address:
xxxx.dedyn.de:port (No address associated with hostname)

I use
IPFire 2.29 (x86_64) - Core-Update 194 and a smartphone (Android 13)
with OpenVPN for Android 0.7.61 from F-Droid store.

I found this Threat.

I have reconfigured:
Globale Einstellungen,
Erweiterte Server-Optionen,
Zertifizierungsstellen und -schlüssel sowie
Verbindungsstatus und -kontrolle

I then downloaded the xxxx-TO-IPFire.zip file,
copied to the smartphone in the download directory and unpacked 5 files there:
cacert.pem
xxxx.key
xxxx.pem
xxxx-TO-IPFire.ovpn
ta.key

My steps are as in the Threat mentioned above:
1:
On the OpenVPN for Android screen there is an icon of a white box with a downwards pointing arrow… I press this and it opens a file searcher on my android phone. I then navigate to the directory I have stored the config files on and select the .ovpn file, which is the only one highlighted.
So I did it.

The app then goes to the Convert Config File screen and you can accept or change the Profile Name that it suggests.
So I did it.

I then press the tick nark at the top right hand side of the app screen.
So I did it.

I am then on the app page showing all the profiles that have been created. This now contains the one I just created.
Exactly.

I press the profile name I just created …
So I did it.

i get this info:

Cannot resolve host address:
xxxx.dedyn.de:port (No address associated with hostname)

What am I doing wrong.

Thanks for help.