Propane Troubleshooting Suggestions?

I followed the line from the curb side over to the street side. There is a rubber propane hose that goes into a brass fitting, which goes into the main regulator on the street side. I removed the brass fitting, and I believe the problem might be with this part. I believe it has a back check valve so propane can only travel one way. There is a rubber diaphragm inside the brass fitting. I tried blowing through the fitting and it seemed plugged. I then used my compressor set to 30psi (the same pressure as the red regulator on the curb side), and no air would go through the fitting??? I'm stumped. Here's are some pictures of the fitting. Does anyone have any ideas?