what is the trick to get offsets to work in mach3?

I have a hobby machine and change the tools by hand, I have offsets in the offset file, and when I do a t#M6 the display shows that the tool# and offset number is active, but the machine does not taking the offset change.  Am I missing a setting or sometning?

there has to be a G43H# (#=toolnumber) in your M6 macro.