The old addage is latex will go on Oil, but oil will not go on latex.
Sherwin and Ben Moore both say that with todays tech and quality of paint, both will cover each other fine.
I still seem to stick to the old saying, But.
your situation could be all these factors or some:
Are you using good quality paint? I do not mean paint from a home center.
Is the existing coat of paint clean of grease and debris and oils? Did you clean it first?
Are you rolling this on or brushing it on?
Did you stirr up the new paint for a good 15 minutes before using?
You might need to rough up the surface especially if its semi gloss or shinnier.
You might need to prime the area first too.
Now, are you thoroughly confused?
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