Clarification: If you have Citadel Plastic Glue - you already have "Plastic cement", it's the same thing. It just depends on the company.
If you're having issues with plastic glue setting on a model, that won't change with new glue (most likely). Remember that plastic glue/cement is normally very liquidy ---- you'll need to have a way of holding the pieces together properly while it sets (allow a day for super solid setting).
Can you take pictures of what is not working on the whirlwind?
If you do end up purchasing "more" plastic glue in the future, avoid Citadel and get something like the following - available at Hobby Town USA, Hobby Lobby or any model-making store (heck, probably even Walmart if they have a section w/ models in it)
Most commonly available brands are Testors and Model Masters.
What you want is the bottle like above - they come with a very tiny precise metal applicator. You don't want the old toothpaste tube of model glue:
^This is a very similar product, but is far tougher to apply lightly --- so skip it!
When applying plastic glue/cement to a join/part of the model you want to ensure:
A) The parts going together fit snugly w/ no gaps (make sure they are filed/fit nicely before applying your glue).
B) Apply a small consistent bead of glue along the seam.
C) Make sure you have a way of holding the parts together for at least 15-20 minutes so they can get a grip on each other. Then allow a day to dry 100% solid.