What is the model number? have you tried searching on the manufacturers website for the manual to see whether this is possible?Example for Samsung TV in link attached https://www.samsung.com/au/support/tv-audio-video/control-tv-without-remote/
The easiest answer would be to purchase a replacement remote for your TV model (check Amazon and EBay, there are specialty sellers) or to get a universal remote. Just make sure that the universal has codes for your specific model
Check the remote control for its infrared emission. Check it with fresh batteries. Check it by pressing all the keys. You can detect the presence of infra-red emission from the remote control, using a cell-phone camera. If you wish to get more details about how to check a remote control, please visit this site. One among the posts has details about it. In some cases, the remote control might need to clean.
http://electronicshelponline.blogspot.com/http://remotesearch.blogspot.com/
Search the site by type in this key phrase "how to test a remote control "in the "search box at the top right of the display window of the Homepage" to get the related post quickly.
https://youtu.be/wUpnETSm6_khttps://www.youtube.com/watch?v=jsSCNCW3IbQ [open and clean]
https://www.youtube.com/watch?v=Qp-l1uh-5gE [open and clean]/