It should be pretty obvious by now, that no one in the audience owns a standalone Internet Radio box.
At least a few in the audience, know how to use computer programs (ones that don't have "radio" in their name), to perform this function. VLC plays lots of stuff. In Linux, VLC is so clever, it can play currently received TV programs from a TV tuner card. It just can't do that in Windows (no code for it). In VLC, you type in the carrier frequency ("216000000") and it plays the TV from it.
But it's still good to discuss the topic, so they'll know what you're on about.
"Not connecting" could be a bad URL, a change of CODEC. You didn't mention whether the affected channels were only BBC or not. Some in the audience, did know the Beeb was changing their setup for this (MP3 codec to MP4a codec, streamed the usual way).
I'm having some trouble playing MP4a on my Windows 11 computer, and this is causing news videos to "disappear" on the web page, to be replaced by no frame at all on the screen. So I am aware that MP4a (some flavour), is a rat bastard of a CODEC. It would not be a surprise if one of your older Internet radios could not handle that and would just sit there silent.
The nice thing about hardware, is it is useless without firmware/software support. I have bought $500.00 gadgets that were obsolete almost as soon as I got them, and then I couldn't use them any more. I've been burned this way before.
Paul