Love this lid for my cup since I’m always on the go

I bought this to replace the lid on my 22oz tumbler. I specifically wanted this style because the slider could be removed for easy cleaning. That part is great, but the issue I'm having is the lid allows my drink to seep from underneath in a slow leak. The silicone gasket thing is in place and properly positioned (looks exactly as it did when I removed it from the package) but has leaked every time I've used it from the first time on.

Replaced my broken lid with this one. It works as it's supposed to.