Both things are probably true.
Head Over Heels is inherently a tough sell. The Go-Go's had a short run as a band, with a few hits along with Belinda Carlisle's solo hits, but they're not a big name group with lots of familiar songs - outside of a relatively narrow age range. The quirky plot and faux-Elizabethan language wasn't going to help attract those very people. I had to talk my wife into attending the show in its San Francisco tryout (she's indifferent about the band), and I knew I was taking a chance. And then we both thoroughly enjoyed it, despite its flaws. We ended up seeing it twice.
Coming to Broadway, they had no stars to sell. The show was going to have to be marketed shrewdly and word of mouth was going to have to be fantastic. It doesn't seem like enough people were aware there was a musical based on Go-Go's songs. The obvious pitch - a fun, exuberantly silly sex farce - wasn't really tried unless I missed something.
The show was drawn a mixed reaction on this board, both in San Francisco and New York, The reviews were also mixed. But given the show's very low numbers, I can't imagine how a bunch of rave reviews would help. There simply isn't a large enough audience for the show. This was an off-Broadway musical that was dumped into a Broadway house after a short out-of-town tryout and no opportunity to make adjustments. I'm surprised the musical is doing so badly, as I am fond of it, but I'm not surprised it's failing at the box office.