Absolute Radio FLAC streams not working

Hi

I am trying to get the FLAC streams from Absolute radio to work on a new Windows 10 Pro desktop with LMS 7.7.5. The lower quality URLs work, such as AAC+ 128k:
http://network.absoluteradio.co.uk/c...s?service=achq

But the corresponding Ogg Flac stream does nothing:
http://network.absoluteradio.co.uk/c...pls?service=ac

I am just entering the URL in the "Tune in URL" box in LMS. Any ideas why it doesn't work?
FWIW, I am streaming iPlayer BBC3 FLAC without problems via Triode's plugin.