Coming from your other topic, have you triple-checked all the formatting niggles that @StJohnLimbo listed? I wrote an extension. Now what? - #7 by StJohnLimbo
I assume you probably did, and they’re in the text which you’re pasting into both venues.
If that’s the case, I might try a bit of copying and pasting in stages for the Mac version (i.e. don’t copy the whole text. Copy a bit of it, paste it over, then the next bit, repeat). And/or just deleting and then retyping a few lines manually, particularly the finicky bits St John mentioned.
I don’t know how often or when the app checks for the satisfactory formatting for an extension app, but sometimes this kind of thing can be teased into activating by not using copy & paste, or using it only partially. Sometimes just the act of typing can trigger it.
-Wade