"... one of my first major challenge ..."

[Odessa Dawn]

Context:

​

Imagine my surprise when I sat down to find that one of my first major challenge was linguistic after all.
Language, Learning and the Essence of Experience | Psychology Today

Is it correct to say "one of my first major challenge was" or should I make it "one of my first major challenges was" please?

​

 

[emsr2d2]

It should be "challenges​'.