shared Add-in works för excel but not for word

[Medes]

Hi everybody,

I have created two Add-ins one for MS Word and another for MS Excel. both
work well.

I have a little problem with that one that is made for MS Word.

if you double click an existing file and open it, my add-in works good and
no problem, or if you open MS Word and click on my button so the add-in works
good here too.
but the problem is if you have already opened MS word and then you go to
File -> Open, and you open an exsisting file , my Add-in does not work, Why?

thanks for your response