Sources connected to the World Dog Surfing Championships, going down in San Fran this weekend, tell TMZ ... the reason Gidget The Pug was not invited back to compete this year -- after winning 2 categories last year, including the Goughnuts Top Dogs Award -- is Gidget's owner's fault.

We're told Gidget's owner was pissed that despite her pooch's victories, she was not featured in press materials or social media campaigns. Instead, WDSC hyped another doggo named Derby ... who's bigger and rocked shades while hanging 20.

Our Dog Surfing sources say the owner was constantly blowing up event staff and organizers demanding Gidget get more promotional face time. Not only that, but we're told the owner was riling up folks in the pug community to crap on the event.

We're told WDSC's top dogs made a call to cut loose Gidget and her owner.

Now, as for what the owner has to say about this ... she feels strongly Gidget was snubbed, but doesn't understand why. The owner claims that after making a simple request to get Gidget's photo in a WDSC press release, the event staff got argumentative and demanded the medals and accolades back.

The owner says she didn't budge on that. She says Gidget also won a bunch of categories in 2017 and claims the pup was slighted then too. Her biggest complaint is the lack of recognition is sabotaging Gidget's shot at a book deal. No joke.