It's one of 2 things...
1) There is a glitch where PMs can disappear and not make it to the intended recipient. However, it's not overly common, especially on such a grand scale.
2) The people you sent them to are just not bothering to respond, which unfortunately happens. When this occurs, given them a few days, send a single follow up that is polite. If you are still met with no response, just move on otherwise you are going to be viewed as a pest. Besides, if they aren't responding to you chances are they aren't interested in your idea and if they aren't interested, do you really want to RP with them anyway? I wouldn't. Best to move on and find someone who does.