Check the remote control for its infra-red emission. Check it with fresh batteries. If it is found OK, check and replace the infrared sensor inside the TV. If you wish to get some details; check the site linked here. It has details about how to check a remote control; by one among the post. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/
If remote control is working OK, the fault should be with the infrared sensor inside the TV. Contact any service technician to replace it. If you're trying to use a universal remote control, it should be synchronized with the TV, with set-up code said for TV. Set-up (Programming) procedure is too much to type in here, and is not practical and it will differ brand-to-brand remote controls. If you wish to get more; check the sites linked here. It has set-up code list & set-up procedure to many popular brand remote controls. One among it has general set-up codes to check with TVs and other devices are given, in the order of the 'device's brand name list' in alphabetical order. Pull up older posts. Search the sites by type in the brand name to your device in its search box at the top right part of the display window. It will help you to find the document easily.