How can we know if you don't post your LTSpice schematic, and your simulation parameters?
What do you mean by "generic opamp models"? Which did you use? LTSpice has a ton of models for real opamps, and even if there isn't exactly the one you're gonna use, just pick something similar.
I don't know what their "generic opamp" does, but apart from having probably ideal characteristics, one thing that will be missing are internal diode clamps on inputs, which may make a big difference if you're not biasing the opamp properly (were you using a single supply?)