apparently the intro scan currently only happens
a) automatically during scheduled maintenance period (see server settings)
b) when manually triggered at the SEASON or EPISODE level (not library, not show).
so, being as this feature was just enabled, it may take a while for one’s system to process their shows in the background.
if you really REALLY REALLY want to have everything scanned RIGHT NOW, go to tv library > ALL > SEASONS
select the first season (checkbox top left), scroll to bottom, SHIFT select the LAST season
3 dot menu > analyze
do be warned, this can put a fairly decent load on your server, so if you have a low powered server and/or large library, don’t be surprised.
