Is there some special trick to forward private messages?

[scarlion1]

I already have instances of tgcf running in live mode and forwarding messages from some of my groups to private channels just fine, but for some reason the private messages from others are not being forwarded.  I even compared the json configs and they're identical except for the obvious differences like forward source and destination.  For source and destination i'm using the Id № that's shown in the other side's profile, or in the private channel's info, with -100 prepended.   Not sure, then, why messages aren't forwarded?  Something to do with private messages specifically or what?  Thanks