Strange Problem - can't find my Players through the (old) iOS Logitech App anymore

Hi;
I have a strange problem:
Suddenly, I can not reach / find any of my players through the old iOS Logitech App.

Strangly, this only happens w/ this old App and using my Atom based LMS (*)
(When I use iPeng or other Apps on Android the Players show up)

Even stranger: When I fire up a different LMS on the same network running on a rpi zero (**), the players are seen via the iOS App!

I rebootet everything a couple of times, updated LMS, reinstalled the iOS App, I have no firewall changed, ....
Can anyone lead me to what to check / what the problem might be?
-> I am currently completely clueless.

Also, It used to work before.

I really would like to get this running again, as I like to have these old iPhones as remotes around in the house.
(I have iPeng, but the old Logitch App was more responsive on these old phones.
Also, I could switch to the much discussed new mobile skin material - but these mobile skins don't run / show on these old phones either, as discussed in the material skin thread....)



(*)
Logitech Media Server Version: 7.9.2 - 1539967036 @ Fri Oct 19 19:17:57 CEST 2018
Hostname: openframe
IP-Adresse des Servers: 172.16.1.103
Server-HTTP-Portnummer: 9000
Betriebssystem: Debian - DE - utf8
Plattformarchitektur: i686-linux
Perl-Version: 5.18.2 - i686-linux-gnu-thread-multi-64int
Audio::Scan: 0.95
IO::Socket::SSL: 1.965
Datenbankversion: DBD::SQLite 1.34_01 (sqlite 3.7.7.1)

(**)
Logitech Media Server Version: 7.9.2 - 1539967036 @ Fri Oct 19 19:20:46 CEST 2018
Hostname: pipal
Server IP Address: 172.16.1.116
Server HTTP Port Number: 9000
Operating system: piCore - EN - utf8
Platform Architecture: armv7l-linux
Perl Version: 5.24.0 - arm-linux-gnueabihf-thread-multi-64int
Audio::Scan: 0.95
IO::Socket::SSL: 2.056
Database Version: DBD::SQLite 1.58 (sqlite 3.22.0)