Don’t know if this is relevant, but when I rip new CDs and add them to my library and want to access them immediately, I have to reboot the Roon server. If I give the server time to ferment the albums will eventually appear on their own.
I know this is not the problem you are having, but the behavior is similar.
never happened, here, in years
Roon core on a dedicated Mac mini or, now, NUC/ROCK. files on a NAS
when I want to play new files right away I perform a manual rescan
if I don’t… they’ll show up many, many, many hours later