Toilets, Sinks, Showers, Tubs and Disposals - Shower Leak

When I run my shower it leaks in the basement around the base between the drain and the subfloor. The subfloor is rotting. I had the fiberglass one peice shower installed recently and everything worked fine for a year. It is now leaking in the basement. I tried putting putty around the upstairs part of the drain but it still leaks. Can anyone help please.
Thanks!

Do you have unobstructed access to the bottom of the shower drain, in the basement? If so, I have found it helpful to start by unscrewing the drain from the pipe under the drain, and taking apart the drain/revent pipes, checking them out, and putting them back together again with proper gaskets and pipe compound under the drain when I rescrew it in securely. Sometimes you can see the leak with a flashlight, and you can tighten up a joint and eliminate it.