Dear Ms.Sue, I am very grateful for your explanation. Please have a look at one more sentence.

"They had been trying for more than ten years to conceive a baby naturally but finally had to resort to in vitro fertilization".
Is the word order OK? Do you think it's possible to use "tried"?
Thank you very, very much.

1 answer

Yes. That's an excellent sentence.

Either tried or had tried or had been trying are correct.