Could anyone help me with the following sentence?

"He had not written a line since he arrived".

As I understand first he had arrived and then he didn't write anything. I think that "He had not written" is a posterior action. Could you explain why it's not possible to write the following way?

He didn't write a line since he had arrived.

Question

Could anyone help me with the following sentence?

"He had not written a line since he arrived".

As I understand first he had arrived and then he didn't write anything. I think that "He had not written" is a posterior action. Could you explain why it's not possible to write the following way?

He didn't write a line since he had arrived.

Answer

the past is hidden somewhere earlier this sentence.
For example:
Yesterday I saw Mike near the office again. He had not written a line since he arrived.
so actually we have
he hadn't written before I saw him.
and
[arrive] and [not write] are consequent actions

Answer

Hi,
Good question. In your original sentence, “He had not written a line since he arrived,” the action of arriving comes first (in simple past), and the lack of writing continues afterward.

We use “had not written” (past perfect) to show the longer or earlier time frame, and “arrived” (simple past) as the reference point.
Your version, “He didn’t write a line since he had arrived,” is not wrong, but it’s less common and sounds awkward. The original version is clearer and more natural.

Answer

Shevelen8 has got the right idea :  the sentence is taken from a text set in the reported past.  "He had not written a line"  describes what has (or in this case) hasn't happened at a time before the time of the report, and  "since he arrived"  shares the same time frame as "he had not written a line".  It would be equally correct to write  "He had not written a line since he had arrived".
If the sentence is not a report of what had happened but a direct statement then  "He has not written a line since he arrived"  would be correct.

Answer

"He had not written a line since he arrived" is correct because:

"arrived" = simple past (the reference point).

"had not written" = past perfect (shows inaction from that point onward).

Your version — "He didn't write a line since he had arrived" — is awkward and uncommon. Normally, "since" is followed by simple past, not past perfect.

Answer

Two completed actions in the past require the past perfect.

"Had I known about the party, I would have gone."