You can NOT challenge any scoring play or turnover, ALL scoring plays and turnovers are automatically subjected to review. If the Browns challenged here it would have been a 15 yard penalty for unsportsmanlike conduct and the automatic review is taken away.
The offense can challenge if their player scored but was ruled short, out of bounds, etc....as long as the official ruling isn't a TD
The defense can challenge if a player not being down before fumbling is ruled down or legally picked off a pass, as long as the official ruling has the offense maintaining possession