After the comics, but before the series.
On 26 August, 2012, the official Zagtoon YouTube channel uploaded a video, "Lady Bug Japanese version", that was described as "Ladybug OAV - Miraculous OAV - Internal use only". The video showed vignettes of Ladybug and Cat Noir fighting a few early villains (Mr. Pigeon and The Mime, who were more silly and more sinister, respectively, than they eventually became in the actual show), plus a bit of their civilian identities. A week and a half later, the video was accidentally changed from "private" to "public," and by the time it was switched back, fans had already grabbed copies and started circulating them around.
The animation was done by Toei, who had done a PreCure movie set in Paris a few years prior and so were familiar with how to depict the city. The short was an attempt by Toei to convince the rest of the development team that 2D animation was the right choice for the series. It's lovely, moody work, but the animators found some of the technical issues frustrating (consistently animating all Ladybug's spots, for instance, was no easier than it had been when Disney did 101 Dalmatians 50 years before), so it was decided to go with computer animation and a less anime style.
The reel would not be officially released until October 2022, when it was included as a bonus feature on a Season 1 + 2 Japanese Blu-ray boxset.
However, that doesn't mean it didn't get referenced. As early as Season 2, Marinette's friend Alya owned a Ladybug animated series DVD, featuring a cover using the PV art.
In Season 3, an in-universe Ladybug movie, Les Aventures de Ladybug & Chat Noir, premiered, with a movie poster based on the PV and clips from the work used as its trailer.
From that point on, whenever a character is watching or even just scrolling past cartoons, it's the Ladybug PV we see.
The PV version of Cat Noir wasn't Adrien yet, but this must get real awkward for Marinette if the part about her civilian life is still in there!