I have a URC-7140 and the same problem with non working Magic-Key.

I found a inconsistent fix / workaround...
...you must try maybe lots of times... You should be a bit resistance of frustration...


NO LED:
In case of pressing "Magic" SHORTLY give NO LED flash. Sometimes pressing Magic does not give at least a single LED-Flash.
Try a Restart of the Remote: Put the (a single) Batterie out and press any Key. Then, put the Batteries again in. The Led will flashes 2x times to confirm start.
?? Not sure: Maybe also shortly pressing any Key or the Magic Key seems to help ??

In case of pressing "Magic" SHORTLY give LED flash:
Pressing at least one time shortly Magic and then long Magic for 3Seconds.
Not working? OK. Try again and again. Try it 5x times or 10x times. It will working...
Example: Also Try pressing at 2-5x time (or more) shortly Magic and then long Magic for 3Seconds.
There is no direct Code or Order or Timing to do this (at least i don't know). Just try.
Good Luck.