Same thing happened to me. To be fair though, I had issues with the app around a year ago and they promptly answered. It seems like they are a bit swamped with support issues now.
We used UserVoice for a while and were responsive, then as we scaled we found it hard to keep up with, and ended up good at our email channel but bad at our UserVoice channel. Since then we've improved again and are generally good at all channels. With this experience in mind, I'd suggest reaching out through multiple channels if you want to get through to them. Try email and Twitter as well as the obvious channel.
I have two Buffer subscriptions, one for myself and one for a client and it has become a must use app.
Good work!
We have plans to make the iPhone app even more awesome (and also include more of the functionality of the web app) so stay tuned for that! Not sure if you have an iPad, but that's on the way too.
Fantastic to have you as a paying customer. Get in touch if you ever have any questions or suggestions!