Closed, orientable, and even-dimensional are irrelevant, as is the condition that all fixed points are isolated. Assume that the action is effective, and that the manifold is connected. Then for every $n>1$ the fixed point set of the subgroup of order $n$ is a submanifold of positive codimension (or possibly a disjoint union of submanifolds of various positive codimensions), so the union of them all cannot be the whole manifold. In other words there is a point with trivial isotropy subgroup.

Closed, orientable, and even-dimensional are irrelevant, as is the condition that all fixed points are isolated. Assume that the action is effective, and that the manifold is connected. Then for every $n>1$ the fixed point set of the subgroup of order $n$ is a submanifold of positive codimension (or possibly a disjoint union of countably many submanifolds of various positive codimensions), so the union of them all cannot be the whole manifold. In other words there is a point with trivial isotropy subgroup.