The game being in ADRIFT is an additional hurdle for testers to overcome, since Inform is more popular–still it’s not fatal. I’d think there is a simple illustrated install guide as well with how to take transcripts, etc.–if not, there should be. I know that I had trouble getting ADRIFT running and wasn’t used to its quirks when it did start running. The error messages were different, etc.
It’s difficult to know what to say when asking for testing. Maybe a few sentences like “This is what the game is about” or “this is what you might not like about the game” beyond the initial description.
Also stuff like “It’s ok if you don’t have the time or don’t like it” is good, as well as “Just let me know what parts flat out aren’t fun.” I don’t know what’s in your letter and it’s not really any of my business, but a small thing like that can go a long way.
But from your signature, I suspect one problem may be that there is too much to do (275 rooms, 30 characters as in your sig is a lot–as is a potential 4-part game. This may make people wonder if they are obliged to, say, work on part 2-4 after part 1) & people don’t know where to start & may get swamped by that many rooms–or feel silly they only got to a few of them! That on top of installing a new app can be tricky.
Now I’ve had good transcription logs and discussions after telling testers (granted, people I already know) something like: Beyond Room 3 is off limits unless you’re really having fun. Just try to get to room 3 for starters and let me know. We can do the rest later. Stop when stuck for 10 minutes because that’s valid data on the gameplay, too.
Or: Grammar bugs are good if you see them, but the narrative is still not set. So focus on what’s fun or confusing in the big picture and don’t worry if you have a lot to say that’s subjective. And don’t feel guilty hammering on a theme. If I’d have seen it, I’d have fixed it.
Or, and this is as noncommittal as their offer to you: I would be glad to return the testing favor if I have time.
Maybe there should be a general suggested boilerplate for authors seeking testers to use? And they could tweak it as needed? I mean, I’ve seen basic outlines, and you don’t want to sound like a form letter, but…just having it there would help an author know what to expect and what to ask.
Because (and this is a bit off topic) I have to admit, for my first game, I was clueless too. I found cold-calling for testers a little scary, and I feel very fortunate some nice people answered my late beta call before IFComp 2011, but that was probably more generically helping someone in need out.
ETA: misread your sig.