Can a scar crossing the cupid’s bow result in not being able to get lip fillers?

Hi Kerris
You can inject into scars that are fully healed. Often the filler doesn't stay in the scar as the tissue is much tighter. Filling these types of areas is more tricky and can require more than one treatment to build an area up with multiple small injections. It is also more likely to bruise ask the area may need injecting more than once.
My advice would be to find an experienced Doctor who is used to treating around scars. You also need to bear in mind that it may not be possible to get a perfect result, which should be covered in the consultation. So you may decide that treatment isn't worthwhile for you.
Hope this works out for you.

Your scar does not prevent you from getting lip filler.  Fillers may even be able to soften the scar, depending upon the nature of the scar contour.  Fillers may also be able to help to recreate a more natural lip border, again, depending upon the firmness of the scar and other factors.

I would encourage you to meet with an experienced injector. They could work around the scar and place filler to give you an enhanced look. Good luck!