Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, there is a partial test to confirm if the old remote is working or not. With fresh batteries correctly installed, point the remote towards the lens of an active digital camera. For every press of any/all button(s) on the remote, there should be a bright light that would register on the LCD screen of the camera.
No light, no infrared transmission from the remote; remote most likely faulty.
On the otherhand, if the remote is good, then consider a possible IR sensor hardware concern in the unit itself.
Please post back results of camera test.