Remote.app not working anymore

Hi,

I'm running iTunes Remote version 4.3.1 on an iPhone7 with iOs11.2.1.

The remote.app has lost its functionality.

I can now only see the iTunes Library logo greyed out.

No way to acces the library.

I have deleted and reinstalled the app.

I have signed out and in of Home Sharing.

I have rebooted the iPhone.

I have rebooted the mac, even in safe mode.

(not necessarily in that order)

All devices are on same Wi-Fi network.

Same app still works fine on my old iPad3 with iOs9.3.5... I'm able to select the library or my Apple TV;

play, pause, adjust the volume and even control my AirPlay speakers...

Very annoying, I use this app a lot!

Any ideas?