I'd heat it up for a while. In general, you do get better quality if you wait it out at a lower temperature, but if it's a question of whether you get the next brew down or not, and your brew is currently not moving at all, then it seems worthwhile.
What I do is to just run hot water into the laundry tub with the brew bucket sitting in it. You can easily boost the temperature to 30ish degrees for a few hours this way, which usually gets the brew moving. Sometimes I have to do it a couple of times.
I presume it does cost you some of the aromatic compounds, but a porter is a pretty robust sort of beer, so I wouldn't worry too much.
It's very often the case that your sugar is not properly dissolved and is sitting on the bottom. I brew in glassware, so it's easy to see that. You might find that giving your brew a good slosh around helps. My approach is to get a circular motion going, and keep that up for 5-10 mins.