This sounds like the classic QSI in La-La land.
This was sent to me many years ago, and has worked everytime for me. Follow it carefully...
The following -may- be your problem.
There are some CVs in the QSIs - that are not available to
you in programming and which are not affected by a reset -
that determine the started/shutdown status of the decoder.
And there is a state (more than one) where they get into
an in between started up and shut down where they will
make sounds but not move. And this will endure across
power ups/downs, moving the loco on/off the layout, etc.
The only way to fix them is to go thru what is referred
to as "the double F9 followed by the double F6 dance".
Depending upon your DCC system a "double" may require
either 2 or 4 presses of the function keys.
And there is a "timing thing" where if you don't do the
double command in the right sequence (duration) it
doesn't take. If you have the timing right then you -will-
hear an "air let off" sound - and that's the only way to
know if you have pressed the right number of times and
within the required time window.
Still another gotcha. The first time you get it to do the
air let off after a double-F9 you still need to wait. At
least 30 seconds or so (until the sound changes that
you hear have settled down completely) ... and then
do another double-F9 ... and wait again. When you are
done the loco should be totally quiet.
Now roll the loco off the rails on one side and keep it
out of contact for a minute or so.
Roll it back down and wait at least 30 seconds. Then
go thru the double-F6 (again listening for the air let
off), again waiting until the sound sequence completes,
doing another double-F6, waiting ... and finally, if this
was the problem ... it will run again.
That in between state is almost always caused by a
long running short that goes thru several retries.
The basic idea is to get them fully shut down and then
fully started up (with a full power off between).
- Hope this helps ... Jim Betz in San Jose, Ca.