First, an obvious question, I hope; are you sure that audio is being fed to the right channel in ACL? How, exactly, are you attempting to feed the audio to ACL and what is the source of that audio, mic, line, etc.?
Assuming you are using Windows itself to pass the audio to ACL, have you checked that its right channel is working normally?
If you are able to give us a lot more information about exactly what it is you are wanting to do, what you have already tried (and with what results) we may be able to offer more ideas or advice. Especially please tell us how you are feeding the audio to ACL.
If you're recording with one microphone plugged into the computer or even an external interface, it will record to only one channel. In the recording parameters screen, click on Mono, not Stereo.