balance does not work on my sonic frontier line 3

I have sonic frontier line 3. I cannot control balance. Can anyone give me advice?
Isn't it called "direct in" on back.
Do you mean volume level balance between the left and right channel?
If so, beside the main volume button, there are left and right levels on the remote. Do these adjust the channel volume.
Balance between the L and R can be achieved on both the remote and the unit's front panel. If this fails, there must be a problem with the unit.