In season 4 episodes 219-220 of the original Naruto, when Naruto and Gaara were being beaten by the resurrected leader, why didn’t Naruto release the power of the nine-tailed fox? Why did he almost die and yet nothing happened? He was one of the weakest people in this fight.
Because that whole arc was filler. Additionally it was a filler arc directed to Gaara, his student and his change. You can say he was the main character, Naruto the side character therefore he was the one who needed to defeat the "bad" guy. If he released the power of the nine-tails I highly doubt Gaara would had the time to shine like he did at the end. Seimei would have been beaten by Naruto.
There is no other reasonable explanation given to us in this arc why he didn't/couldn't use it. You could say it was due to plot.