I think the guys got you covered, but just in case you are having one of those "but I cleaned it" moments, (been there) undo the needle Chuck and gently move the needle back and forth by hand, if it feels spongy or doesn't move smoothly, then it isn't clean.
If you are 100% certain it is clean, then check how far the needle is sticking out the front of the nozzle. If it seems longer then your nozzle may have flared. (Also if it seems shorter, it's another sign the nozzle is dirty.) A flared nozzle will need replacing.
Once you have it sorted, get some createx 4012. Not only is it a great reducer, but after you've cleaned your brush run a little of this through, it's an awesome cleaner, and will get anything that's missed. Do it on white paper (or black if using white paint), and make sure it comes out clear. If it's not clear, it's not clean. Once you have your routine down, a couple of drops of 4012, will be all you need to keep things flowing.