It's not really a properly defined question because there's no single good definition we can apply for "back to normal" if you mean "when did fern spores get more common than fungi and the light levels return to normal again" (a few years) the result is very different than "when did the 80 tonne herbivores and 8 tonne predators re-evolve?" (66 million years and counting).

IIRC it took something like 5-10 million years to get any mammalian herbivores over 500 kg coming back.