Deleting an Old Port forward with no associated device

I am trying to delete some old ports that I forwarded a while back from an old laptop that I no longer have but every time I try it always just give me the "We're having some trouble" error, this has only been happening ever since you can no longer type in the default gateway to access port forwarding. What Can I do so that I can delete those ports so they can be added to a new device?