D400 remote app “connects” on iPad and iPhone but won’t actually adjust anything?

[Gigantorex]

Hi
I’m having gremlin issues lately with Roon and a separate issue with the Dev remote app.

The remote app actually does connect and is visible on the iPhone iPad but doesn’t actually function at all.
Eg. The volume rises on the iPad app but doesn’t change the sound setting on dev.
I select the USB on the app but doesn’t swap to USB on the dev?

I’m guessing there’s a simple solution - anyone know what it is?

The hard expert remote works fine though.

Thanks
Alan