The character's muzzle was made by cutting a cube in half and making it mirrored and shaping it how I wanted before I duplicated, flipped the object and then fused the vertices together. Now there's this...seam?

I can't get rid of that bump in the center no matter what I do! I tried reshaping it, adding more loops, moving the center loop etc.
Anyone have a solution for this?

I'm considering restarting that part at this point tbh! BUT I want to figure this issue out so I can fix it in the future.