Maple Porter Re-Pitch?

So, tried to come up with a recipe for a maple porter. Waited to add maple syrup until secondary. Fermentation stopped at 1.025. Since it wasn't fermenting any further, I kegged it and carbonated it. Good flavor, but almost a little too sweet to be really drinkable. Taking it off the tap, warming it up, bleeding the pressure, then re-pitching some yeast once the beer went flat. Any reason why that won't work? Never done this before, and wonder if having kegged and carbonated it already will pose any issues.

If you do it, you can't just pitch some yeast in - they need to be active. You'll have to make a starter, and pitch it at its height of activity.

I realize that. I made a starter for this beer when I made it. Not sure why fermentation stalled out. Thinking I added the syrup too late, so the yeast weren't active enough to respond. Simply making sure that I'm not missing anything that would prevent the re-pitch from working.

Recipe. Maybe it's done.

Maybe it got cold and the yeast dropped and then you racked to secondary leaving most of the healthy yeast behind.

Take it off the tap, and into a fermenter, and place in a warm location. Add a few ozs of sugar (dissolved in a little boiling water), place on an airlock. No new yeast. If fermentation takes of in a couple of days, you have plenty of yeast and the beer is done.

If you have yeast, it will consume the simple sugars, but may be at it's limit for complex sugars.