I didn't notice until now that he left - past simple or present perfect?

Question

I have thought that that when something that I can notice continues up to the present, I should use present perfect. For example:

I have not noticed until now that his car is white.

When the action I could notice happened in the past, I need to use past simple:

I sent him the wrong report and I did not notice until now.

But in the sentence I didn't notice until now that he left, I am not sure whether it is the first case or the second. I tend to think it is the first, as he left and his "being gone" is still valid, so I would say the present perfect should be used..is that correct?

Which one is correct and grammatical?

Answer 1

You should use the past perfect:

The past perfect refers to a time earlier than before now. It is used to make it clear that one event happened before another in the past. It does not matter which event is mentioned first - the tense makes it clear which one happened first.

https://www.ef.com/wwen/english-resources/english-grammar/past-perfect-tense/
(emphasis mine)

At one point in the past he had left but you only noticed afterwards. So it should read

I didn't notice until now that he had left