So much for being pulled out of the dead pool. TuneWiki, a popular social music app with millions of users that let people see the lyrics to songs they were streaming on Spotify and other platforms, may have finally sung its last song.

After announcing in July 2013 that it would shut down, it then got acquired at the 11th hour, as it turned out by private equity firm Vert Capital, which continued to operate the service. Yet now TuneWiki has gone completely offline after a source described it as going delinquent on paying bills and getting the plug pulled on its servers. (In fact, the TuneWiki links above are WayBack links because the originals are no longer there.)

It’s a somewhat surprising end for the app, considering it was one of the most popular apps on the Spotify platform — a fact confirmed by Spotify itself, whose spokespeople I contacted asking if the company knew what had happened (they did not). Close to the time of shutdown, TuneWiki had over 10 million active users in 70 countries, playing over 8 million songs each day and having over 1 million social interactions each month (interactions include comments, shares, likes, follows and lyric art).

Other services that integrated with TuneWiki included Slacker and Deezer along with apps for iOS, Android, Windows Phone and preloads for specific carriers and other devices.

Unfortunately, ubiquity does not always equal business success. By the time that Vert had approached TuneWiki, the startup — which was founded in 2007 and had raised $10 million from the likes of Motorola, NTT Docomo and Benchmark — was unable to raise more funding and didn’t appear to be making good enough returns from its free, ad-based services. Plus there are other competitors, like musiXmatch and others. Vert, we understand, paid a mere $115,000 for the company, assuming everything including assets and stock in the process.

Sidenote: Vert Capital’s MD is Adam Levin, who you may recall was, at Criterion Capital, also the person behind both the acquisition of Bebo from AOL in 2010, running Bebo for a period of time. Later Levin also acquired PoolWorks from Holtzbrinck Digital. PoolWorks was the name of the company that included various German social networks, including StudiVZ, sometimes called the “Facebook of Germany.” Both companies are listed as a part of Vert’s portfolio today alongside TuneWiki.

After the sale to Vert, most of TuneWiki’s employees were let go. Some, like director of engineering Jared Fleener, appear to have stayed on, while an interim CEO (Seth Gerson) was brought on “to try and flip the company,” our source says.

Then, a difficult situation seemed to get worse. In the past 2 months, “Vert has been delinquent on many of TuneWiki’s bills,” the source says. “As of [Monday], the datacenter pulled the power on the equipment due to delinquent payment. It would seem Vert has elected to let the company die.” We have tried to contact Vert Capital and its MD Adam Levin to ask about whether this is indeed what’s happened. We will update as we learn more.

It’s a curious end to the company, if this is really the end. There are assets: at least one patent, datacenter equipment, the company’s Lyric database and its user database, along with “several terabytes worth of user metrics.”

In the meantime, users appear to be slowly realising that the lack of functionality is more than a small blip: here you can see their reactions interspersed with the usual bot-fuelled Twitter marketing spam.