Hello Achim,
in addition to the above: if you start the CCAS App (CCAS App) on its own first and take a look → do you see Traffik in the app? Have you, in VFRnav (VFRnav) under Settings → Traffic data → Altitude filter + Radar range, defined these where applicable?
Happy flying,
Karsten
Hello Hermann.
Both on the same device. As I said, everything works fine at my place.
I’ll drive to the airfield again this afternoon and try it out. I’ll let you know then whether it worked.
Regards, Achim.
Those are good tips too 
Otherwise, post a screenshot here of the VFRnav settings “External data source”.
I’ll go to the airfield again this afternoon
In the quick settings at the top of your device you can turn off the Wi‑Fi. That’s the same as being at the airfield with no Wi‑Fi. That way you can test it at home too 
Hello Sven,
I turned off the Wi‑Fi and no longer have any displays. In the Status section in VFRnav under the settings for data sources it says: Connecting…
When I turn the Wi‑Fi on, it says: Connected and I then get the traffic displayed.
Now I’ve turned off the Wi‑Fi again and changed the startup order : first VFRnav and then CCAS and now everything is displayed, even without Wi‑Fi.
Problem solved!? 
…No, the order doesn’t matter!
just to double-check:
…does your config look like this too?
For checking: was the app running correctly in the background? …or when you brought the app from the background to the foreground - did you have to confirm the rules again? …if yes, then it wasn’t running in the background (I had that with a mate who had a Sony phone… searched for ages, it was a permissions problem)
…
Apparently that was the problem. I’m now at the airfield and everything is working perfectly.
Many thanks to everyone for their help.
Kind regards, Achim
Now that everything is working perfectly, I tried this on a flight.
At first I got a fright when an aircraft appeared on the screen directly at my position, but I couldn’t see one nearby. On closer inspection the displayed aircraft had my registration, D‑EZYC. So my aircraft is shown twice, although not at all times. Is that normal?
Hello Achim,
that’s normal and correct by default.
Please click on the CCAS symbol at the bottom left and read through it….
…and now have fun!
Happy flying,
Karsten
Hello Karsten, I’ve found it. Why is the icon rotating and not showing the correct flight direction?
Regards
Achim
Morning Achim,…
…I still don’t quite understand what you mean? ..do you mean the compass rose with the symbol? …
Pilot greetings,
Karsten
The light-blue aircraft symbol with the identifier ..YC should be pointing in the direction of flight, like the dark-blue one in VFRNav. It also rotated in different directions.
Regards
Achim
…it should be overlaid on the VFRnav symbol and “move with it” — yes. …does it stay like that all the time, or does it “jump”? …sometimes correct, sometimes like that?…
How does that look in the CCAS?
…
… it keeps jumping back and forth, at times it’s completely gone …
…as a remote diagnosis I would say that this points to unstable data deliveries of the CCAS data. The data are transmitted via mobile data, after all. Clarification: isolated case? Check on the CCAS monitor display → does it jump here as well?
Aviator greetings,
Karsten
I’ll keep an eye on this on the next flight to see whether the CCAS monitor display is the same.
Flying regards from the Westerwald
Achim
Thanks Achim and please report back.
Note: Apps like CCAS or SafeSky are great! ..but they will never be able to replace on-board systems like Stratux or Powerflarmflex or even offer the same quality.
Clear skies,
Karsten