Translation:I would like to take a break.
Whilst I wouldn't say your sentence is wrong, I think it's a bit misleading and I see why it was rejected. It's quite easy to mistakenly think "一下" means "a bit/a while/a little" but it doesn't at all. It's just a way of softening the tone of the sentence to sound less demanding and more polite. (Especially when making suggestions to people or asking for favours).
Exactly what I wanted to say. Just reported too. "I would like to take a break" is so formal for such a casual phrase. I'd translate this even more colloquially as "I wanna rest a bit"
I think "I want to rest" can be accepted, albeit a bit less verbatim translation.
“I would like to rest a bit” also works. I am not complaining at all btw, I am just saying that is another correct translation.