In my experience brown patches are usually where the treatment has killed off the moss etc. Hopefully it's just the product doing its thing and a few weeks later you should see results once the new growth has kicked in.

However, it could be that way if too much product was applied. Did you use a spreader/or follow guideline amounts?

One year I randomly applied some of this by hand and ended up with some really vibrant green mounds of growth - I now own a spreader...

On a related note, have you scarified the lawn to remove the old dead growth? It can make a world of difference and you'd be amazed how much comes out.

If the brown patches are just where moss has been killed, then rake out the dead moss. You will need to wait six weeks from the day you applied the treatment to reseed those bare patches. Not sure it will be dead moss though, that usually turns black, not brown, once treated, so the likelihood is your patches are caused either by uneven application of the product or because it wasn't watered in within 4 days if there was no, or insufficient, rain, or there were patches of weeds which have been killed. Or you've got a dog, particularly a bitch...