I was answering a mail from tech support and wanted to tell them that I had already sorted out the problem I intially told them about. I also wanted to emphasize that I had tried the solution suggested in their mail before writing them. Given that situation, which of the following sentences is correct? "I have tried that", "I had tried that" or "I did try that"? Note that I'm referring to something that happened before something else that's also in the past, so I guess I have to use ... past perfect? Please explain to me which of the sentences above is correct and why. It would also be nice to know if, in this situation, it makes a difference whether I am writing about something that I tried or something that I tried before writing the first email. Thanks in advance!
If I understood the sequence of events correctly, your letter should look roughly like this:
I'm writing to report that I've already sorted out the problem. Thank you for the suggested solution. I had tried this solution before receiving your letter though.
Using the Past Perfect is okay here: you're mentioning an event in the past: trying out the solution, and then a subsequent event: receiving their letter.
You may use did try to put more stress on the fact that you tried this solution:
I'm writing to report that I've already sorted out the problem. Thank you for the suggested solution. I did try this solution before receiving your letter though.
But did try would look better in a letter telling that you still haven't sorted out the problem, as a way to reassure them that you've indeed tried it.
If you use "I have tried that" it will look ambiguous: the construction will leave them guessing when exactly did you try the solution: before you received their letter with the suggestion or after.