Keep working it in more.
I bought a store bought cube and it sucked.I lubed it up and it was great.
I then did some modding to it and it was even better.
What cube is it?
Getting the lubricant to work into the cube often takes some time. I usually find that the cube starts out sticky-feeling but very gradually becomes smooth and fast; sometimes taking half an hour or more.
Maybe you used too much or too little spray, or sprayed it under the wrong conditions (temperature, humidity, distance).
The more you use silicone, the more time it takes to dry. Sometimes it is necessary to put loads of silicone, if you have a puzzle that requires it (like megaminx). You can also fasten the process by using hair dryer (if you have one). I actually use a vacuum cleaner (the part where hot air comes out), because I don't have hair to dry .
Well, yeah, the time you spray the lube on, it feels like you did something wrong when you play with it...
My advice: take it all apart and clean it a little, put the pieces back together, spray enough lube in each side (R turn, U turn etc), turn it a bit so that the lube goes everywhere and leave it alone overnight!
When you wake up it will be fantastic!