If the buttons are worn out or dirty no amount of resetting anything will help. A surefire solution is a new remote or you can use the mobile app as a remote:
Also I barely use the remote, so I’m not sure why it would be worn out or dirty.
Tulie, any of the current Roku remotes (except the one specifically for TVs) will work with your 3920. You can verify whether the current remote is transmitting when you press a button by pointing it at your phone's camera. You should see a flash on the phone's screen when you press a button. If the buttons aren't worn out and are just dirty (sometimes it's inactivity that's the problem), it's not easy to take a remote apart, but it's possible and using some rubbing alcohol and a Q-tip to clean everything may help.
Roku remotes: https://www.roku.com/products/accessories
Many universal remotes also support Roku devices.
