Replacing Gasket on a Stovetop Espresso Maker?

We have a stovetop espresso maker. When we replace the rubber gasket, the machine stops brewing. We tried wetting the gasket, tightening it, etc. to no avail. Then after a few failed attempts the thing starts working and consistently so. Any ideas about what is going on and how to avoid this trial and error. Thanks.

By Christopher Flores from Oakland, CA