Music library - no authorisation / access from certain speakers

Hi All,

I’ve been perplexed with the following problem for the last 6 months, wondering if anyone can help.

I have a 12+ unit system (speakers, amps, connects etc) mainly connected via ethernet lan gradually built over 3-4 years.

the music is library is on a nas box.

My problem is that “all of sudden” most of the speakers are unable to access the music library even when I delete and then re install the NAS music library.  I get a “no authorisation” or “cannot access music library” message when I try.

if i create a group and include one of the first speakers originally added to the sonos system the music library can be accessed.

any ideas on how to solve this annoying issue

thanks in advance