John Carney struck gold with “Once,” the not-quite-love story of an Irish troubadour and a Czech immigrant in Dublin that charmed audiences in both a 2007 Oscar-winning indie film and then in a stage adaptation that won the 2012 Tony Award for Best Musical.

And now his underrated 2016 indie gem “Sing Street,” the retelling of his own experiences with his teenage new-wave band in 1980s Ireland, is getting its own stage adaptation at Off Broadway’s New York Theatre Workshop, where it opened Monday night on the same stage where “Once” premiered eight years ago.

Like the previous Carney adaptation, the show features a book by playwright Enda Walsh, a barebones set and a talented cast who play their own instruments on stage.

While director Rebecca Taichman’s production offers moments of transcendence, particularly in the often-luminous second act, the show needs needs some additional polish on its hero’s defiantly brown shoes.

Taichman and Walsh effectively convey the economic despair in 1980s Ireland, as citizens fled overseas for job opportunities and those who remained struggled. Our almost-16-year-old hero, Conor, is pulled from his school because his squabbling, on-the-edge-of-divorce parents (Billy Carter and Amy Warren) can no longer afford tuition and he’s dispatched to a free school run by a bully of a Catholic brother who’s not above a little corporal punishment to reinforce his rules. That includes requiring students to wear black shoes — even if, like Conor, they can’t afford them.

Once there, Conor decides to form his own “futurist” rock band — partly out of a musical passion shared with (and at first lifted from) his older brother, Brendan (Gus Halper), a twentysomething agoraphobe who has not left the house in several years, and partly to impress the too-cool-for-school Raphina (Zara Devlin), whose front of model-like poise masks her upbringing in a broken home and willingness to hook up with much older guys.

The main problem is that Walsh and Taichman don’t do nearly enough to adapt the film’s complicated plot to a new medium, or to find theatrical ways to stage the various events. (A large screen dominating the upstage area would have been a great place to show the teenage band’s hilarious efforts to shoot MTV-ready music videos, for instance.)

The band itself has more members in the film — but few of them seem to have names, let alone backstories. Johnny Newcomb’s class bully, already a teen-movie cliché even before he surprises Conor with a kiss to suggest closeted homosexuality, could be jettisoned altogether. And why bother giving bandmate Eamon (Sam Poon) an onstage pet rabbit if the poor boy gets just one more scene with Conor (and the bunny goes MIA as well)?

Streamlining the story would allow the material some breathing room, and an opportunity for the key performers to shine. Brenock O’Connor, a 19-year-old “Game of Thrones” alum whose Olly famously stabbed Jon Snow in the heart in Season 5,  gives an appealing performance as Conor — whose ability to feign confidence is as striking as his dimpled chin and unruly mop of brown hair. (Though Conor is the center of the story, the show opens with Brendan — for reasons that are never made clear.)

Conor is a classic rebel, challenging the rule-bound strictures of Brother Baxter, his warring parents and the woeful economic conditions in his native land (not to mention gender norms for the period). And as he’s finding his feet, creatively and personally, he’s seeking solace in his brother (himself crippled with self-doubt), his budding romance with out-of-his-league Raphina — and in his music.

The tunes, written by Carney and Gary Clark, are a mix of “Once”-style ballads and catchy New Wave pastiche (with period classics like Depeche Mode’s “Just Can’t Get Enough” tossed in for good measure). And while the onstage musicianship is often spot-on, the sound mix wavers so that the lyrics sometimes get garbled. (Since this is a fledgling amateur band, perhaps the lo-fi effect is intentional?)

Devlin’s Raphina has the look and attitude of a teenage femme fatale, but she pales in comparison to her movie version, rising star Lucy Boynton (of “Rocketman” and “The Politician” fame). And sadly, her voice is just a little too wan for Raphina’s big numbers. (In fairness, Boynton merely had to be sung to.)

Still, there is a lot to admire about “Sing Street” — and a little buffing could turn Conor’s woeful brown shoes into Broadway-ready kinky boots.

Read my full review at TheWrap.