Hello and welcome to JustAnswer! I am Pete, a TV expert, and I'm happy to assist with your question today.
Celestial are the manufacturers of your LT1918HD TV.
Not all universal remotes will have a specified code for Celestial TVs.
It may be possible to manually program the remote, depending on what type you have.
If this does not work, then you would need to get a replacement Celestial remote.
These are occasionally available on eBay and other sites.