The tags are split between seasons, I assume you were just looking at the fire_force tag, which only encompasses posts from season 1.
S2 tag:
https://www.sakugabooru.com/post?tags=fire_force_season_2+
Series tag (encompasses both seasons):
https://www.sakugabooru.com/post?tags=fire_force_series+
S2 tag:
https://www.sakugabooru.com/post?tags=fire_force_season_2+
Series tag (encompasses both seasons):
https://www.sakugabooru.com/post?tags=fire_force_series+
Oh, well. I'm stupid. Thanks for the help anyways.
GoldenMonkey
Why are there no Fire Force Season 2 clips?