It’s hard to answer without seeing the assembly. I’m not familiar with the Novi drain plug –
But to take a guess – if you’re handy – you should be able to unscrew the *entire* drain plug assembly from the tub drain.
(I’m talking about the entire assembly, which includes the chrome or brass ring around the drain plug. Assuming the tub is fiberglass, then you have a ring around the drain of a different material – usually chromed. That whole ring can be unscrewed and removed.)
Removing the whole thing may or may not be difficult – it depends upon if you can get a grip on it to turn it. And replacing it, you’ll need to put some plumbers putty around the hole before screwing it back down. (This is not difficult) Make sure it’s screwed in tightly.
This is all assuming you can’t get the stopper out – Again, I’d have to see it to know why the stopper won’t come out.