I have an acrylic shower pan that I'm using with an Oatey "no caulk" shower drain. I installed it as advised by the instructions, but it's leaking between the top flange and the shower base. Surprisingly, the "no caulk" rubber gasket is holding up just fine. In other words, the silicone joint is leaking.

It would appear the original poster in this thread had the same problem:

Does anyone have any experience with these drains? I am on a concrete slab, so there is no access underneath, and so it would seem I need to tear out the shower pan, remove the drain, and try again. I am hesitant to use silicone sealant the second time around, though.

This pictures shows how the inner part of the drain is holding water, while the outside flange area is not. Note that I did apply silicone underneath the flange, and wiped away any and all excess (you can see it slightly).

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