Paint Not Sticking to Wall

Here I’ve covered the wall (pale blue area) with wallpaper primer. Because I want to avoid the light wall from showing between the seams should the paper shrink as it dries, I’ve striped under the seam area with diluted dark paint from the hobby store.
But you can see there are areas where the paint is not adhering. What’s up?
The original surface was a gloss paint. My wallpaper primer will stick to gloss paint. But in this case, some small areas were missed when my paint roller passed over it.
Then when I swiped on the dark paint, it adhered well to the matt finish of my primer. But it could not grab ahold of the small areas of gloss paint peeking out from under my primer.
If this were a large area, I would be worried. Because wallpaper paste doesn’t like to stick to glossy surfaces, either.
But the areas of gloss not covered by my primer are minimal, and won’t interfere with adhesion of the new wallpaper.

Tags: adhere, gaps, gloss, glossy, hobby store, not sticking, paint, paste, primer, shrink, sticks, wallpaper