Pairing up Margot Robbie and Colin Farrell for a big screen fantasy romance doesn’t pay off in “A Big Bold Beautiful Journey,” a film that has one or two big moments on its road-trip-romantic “journey,” a little digitally augmented “beauty” along the way, but little that measures up to anybody’s idea of “bold.”

Robbie, perhaps in an attempt to shrug off “just a beautiful face” pigeon-holing in Hollywood, doesn’t do romances. And Farrell, bless his heart, decided not to have a proper shave for this role. But they’re game and light when they need to be even if the heart’s-sad-baggage story lets them down.

David’s a 40ish single doing all right for himself in his solitary life in an unnamed Left Coast city. But a road trip to a weekend wedding might be foiled by that parking boot on his tire. Serendipity delivers a flier for A Rental Car agency, close enough to reach on foot, tucked in an alley in a cavernous warehouse.

Phoebe Waller-Bridge is the German-accented potty mouth who runs the place, which only rents 1994 Saturns. Kevin Kline is the wise old mechanic who keeps them running.

David will be “f—-d” if his “phone craps out,” so she gives the option GPS the hard sell.

They take his photo but she already has a head shot on file. She thinks he’s an actor. He’s not.

“Ve perform more than ve tink ve do,” she purrs in her best Beer Hall Putsch accent, which comes und goes.

“Sometimes we have to perform to get at the truth,” the Oscar-winning mechanic philosophizes.

Sure enough, David needs the GPS, which starts communicating with him directly on the trip. That’s how he’s paired up with another ’94 Saturn SM driver, Sarah. They’re thrown together when hers won’t start.

They’re both determined to stay single, so they can flirt at the wedding. But she’ll dance and he doesn’t dance. He can smile, make eye contact and ask questions, but she isn’t having it.

“Stop trying to be charming…I’m afraid of hurting you.”

Even though she hooks up with someone else at the wedding, they’re back in the car whose GPS has a mind of its own. It’s when it directs them to stop in a forest where a red door in a doorway to nowhere beckons that the magical realism kicks in.

Such doors will take them in a corner of each other’s past — sad, teen traumatic, wistful and the like.

When the second door hurls them into David as his 15 year-old self, a grown man determined to warn the co-star he crushed on in their high school musical of her “future” with the lout she prefers to be with, “A Big Bold Beautiful Journey” peaks. Too early, it turns out.

“How to Succeed in Business” is derailed, mid-opening night, by a singing, dancing David who carries his pleas to his crush onstage for all the confused audience to see. Luckily, “musical nerd” Sarah is there to bail him out.

After that moment, “Big Bold” ebbs. And all the sadness interrupted by jokes that follow can’t equal it or top it. The Seth Reiss script devolves into a series of “We can’t date” arguments that can’t transcend cloying.

The journey, contrived by The Rental Car Agency and its all-knowing GPS, is to resolve their “issues” and offer closure about this unrequited love or that parent you never got to say “goodbye” to.

Sarah’s cynicism and David’s emotional detachment must be explained and reconciled in Psychology 101 terms.

And what could have been a wistful/hopeful light-hearted romp just slogs up and down a soggy West Coast Interstate with the odd stop for a CGI sunset as viewed from a lighthouse.

The “doors” are a trite device, and the high school, lighthouse, after hours at a museum, hospital etc. they lead to are rarely magical.

The casting coups suggest this might have seemed frothier and more fun on the page. But director Kogonada — the John Cho trapped in “Columbus” Ohio dramedy was his — wasn’t having that. He leans into the “learning” and smothers the life out of the fantasy.

Waller-Bridge may earn the picture its R-rating all by herself, but her f-bombs quickly lose their comical sting.

And there’s only so much twinkle in Robbie’s Sarah warnings to David she’ll “hurt” him, his plea that “Maybe I’ll hurt you” and Robbie’s side eye, with the implied “Look at me and tell me who’ll hurt whom, near-beard boy.”

Rating: R, profanity

Cast: Colin Farrell, Margot Robbie, Phoebe Waller-Bridge, Hamish Linklater, Jennifer Grant, Lily Rabe and Kevin Kline.

Credits: Directed by Kogonada, scripted by Seth Reiss. A Sony/Columbia release.

Running time: 1:49