You have great advice already. It's hard to answer this without knowing more about the work. Here's the link to Online Critiques:
https://www.scbwi.org/boards/index.php?board=121.0.
I've also written something that I thought was a picture book that turned out to be an outline for something longer. Consider the emotion in the piece and whether it's in there. If not, there's a good bet you have an outline for something longer.
Further tips for cutting (and some repetition of what's been said):
Watch for repetition. This can be great in PBs, but it has to serve the story.
Watch for telegraphing. This is when you tell the reader something will happen and then show it happening. "Jenny will go to the store. She gets in her car and drives a few blocks. She parks in front of the store." They say you should show and not tell, but if nothing important happens on the way to the store, this whole thing can be replaced. "Jenny went to the store." (Make every word pull its weight and every scene be worth its weight in words.)
Cut things that will be illustrated unless they matter. Lilly's Purple Plastic Purse will be shown, but the author (Kevin Henkes) keeps the two descriptors. They matter to Lilly, are fun to read, and even warranted inclusion in the title.
Focus on a single plot with maybe one minor subplot. (Often subplots in picture books are only in the images.) More than one plot is a sure sign of work for older readers.
Stay in the POV of a picture book aged reader. (You can stretch the language with an omniscient narrator but your themes and main character have to fit this target---childlike adults and objects/animals are substitutes for the child reader.)
That's all I can think of off the top of my head. I hope it helps.