The Tap Tap Revenge closed all it's servers and removed all it's apps from the playstore/app store officially since February 5 2014. Reason being obviously the lack of engagement that they were getting more and more of.
Their Facebook page said

"it no longer makes sense for us to maintain the Tap Tap franchise”

The mobile and music market has changed a lot since the inception of the franchise 5 years ago,6 almost, I am guessing their business model wasn't able to keep up with it. But in it's defence I have to say that there was no game on Android or iOS like the TTR series. What they needed was one major revision of their outlook and things could've been back on track
But as someone who has played all versions of the game I also think this was a fitting end, the game played it's part out perfectly and didn't try to force new versions every year in order to extract money out of their fan base.
RIP TTR