Hi Markus
Maybe there is a problem with world traffic, I can't test it because I use Traffic global. I just saw that you need the new world traffic beta with the newer TCAS option, you can find it here:
https://forums.x-plane.org/index.php?/forums/topic/223767-wt-320rc4-for-windowsmac-for-all-versions-of-xp-11-with-or-without-vulcan/
Another option just for testing is to download the free Live traffic plugin and set there the TCAS option to on.
https://forums.x-plane.org/index.php?/files/file/49749-livetraffic/
I tested this, too and in Pilot2ATC I can see all planes. So you can find out if there is a problem with P2A or the traffic plugin.
In my cases, I can also see all traffic on the original x-plane Map, activated by "m" key. In Pilot2ATC the new Traffic option is working well for me. Hope this helps.
Regards, Yannick