When I brought Agent Nibbles and the Mop home, Mop drank just fine but Agent Nibbles literally just would never drink. We started panicking. Wetting his veggies, and stuff.
A month later, I moved their water bottle down a couple notches.
Suddenly, everything was fine, he started drinking just like normal.
Stubborn little guy. He wanted his water positioned JUST SO.
Anywho, I doubt that's the case but it wouldn't hurt to move the water bottle around a little just to see? x)
Best of luck!