Heyo, I’m thinking you may not be a native English speaker? Your sentence was nearly perfect, but you got the wording a little wrong, which is what made me think that may be the case.
For reference, it’s either “didn’t know” or “never knew” with the latter being a longer amount of time. “I didn’t know I dropped that dollar bill” vs “I never knew Santa was an alien.”
Just wanted to hop on and let you know in hopes of helping you improve. _