Yeah been there done that. All you need to do is repaint the door with Old Masters Graining Base and start over.
Find a fiberglass door and match the original color again. Will look similar to this photo or the 2nd or 3rd photo. (most likely the 3rd)
To save you the run around, I shot this photo below for you showing Old Masters Graining Base in Maple which is a great color to match many stock fiberglass doors but will note MAPLE color is also limited to a range of stain colors. For example you dont want to use maple for red mahogany stain colors, use Walnut Base instead. Also Maple isnt good for natural or super light stains, use a different lighter pale graining base color. Regardless, this graining base will give you a sheen and finish very similar to original non-finished fiberglass.
If you want to get technical, use a base color for the stain color you need and use ZAR brand Solid Stain rather than Gel. This way you can apply the stain as you would apply any solid stain and do it as if you were painting a door rather than ****in around like you are painting a mona lisa.
Below is a metal overhead garage door I stained using ZAR to match a fiberglass door. Can shown is stain used. I stained that overhead door in under 20 mins to give you and idea how easy ZAR Solid Stain is to use.