What is the past perfect progressive tense of the verb "try"?
"Had been trying"
The past perfect progressive tense indicates a continuous action that was completed at some point in the past. This tense is formed with the modal "had" plus "been", and the present participle of the verb (with an -ing ending)
"I had been working in the garden all morning."
"George had been painting his house for weeks, but he finally gave up."
So the past perfect progressive tense of try, is "had been trying".
"We had been trying for weeks to get pregnant."
Hope this helped!