The remote should work as long as its within 10-15' of the unit. If you have to be closer, your battery might be getting weak - either the battery in the controller, or the one in the drive. Make sure the drive battery is fully charged and depending on which remote you have either charge it, or replace the battery. (see About the Remote Control Battery)
Note, when you turn on the main unit and the remote you should wait about 10 seconds for them to initiate and sync up, once they've synced (the remote will vibrate and the unit will beep when they have) you should be able to start running. As long as you're within about 10-15 feet of the unit the remote should sync up normally.
If you are experiencing "ghost running" which can happen when the remote isn't given enough time to fully pair with the unit upon turning it on. Just turn both the remote and unit off and back on again and allow time to sync before trying to operate the drive.
For a review of how to sync the remote see this article: Things to know before or as you're setting up!
If it's still not working right, please contact Customer Success by clicking the help button