In my opinion the first sentence sounds betterOriginally Posted by Nordic Bill
I tried my powers of persuasion but it did not work [ refers to the action stated by the verb :I was not able to persuade her]
the second sentence: "I tried my powers of persuasion but they didn`t work " is not so good as
" I tried my persuasion powers but they didn`t work"
or even better: " I tried to persuade her but it didn`t work."
This last sentence is best of all, in my opinion.
Student or Learner