I'm not from Oregaon, so I didn't get one but...
1) What is water-ball?
2) are they paid or volunteer? if volunteer, whomever might have gotten the mail yet. or they don't know #6, and havn't responded
3) did you specify what the entry fee was for? if not, they might think it's money that could be spent better elsewhere.
4) maybe there members have other things that need to take precedence over a tournament (like answering calls)
5) it might be too far for them to travel, especially considering #6
6) They might not know what a water-ball tournament is