And the issue came back. I did absolutely nothing and can't connect to the 271 again.
The IP address I defined in the app was gone. I didn't do that but it's gone.
I added and deleted and added it a gazillion times and it makes no difference.
This app version ...

Main: Marantz Cinema 50, Meridian 271, DSP7200.2, DSP5200HC, DSP5000 rears, Meridian 210.
PC/Headphones: Mytek Liberty II, Sansui CA-F1, Sansui B-2301, Sennheiser HD800, Kef R3