setState is an async operation, it doesn't update the state immediately, But the setState callback, has the last instance value from the state, So.

ComponentDidMount() {
if (this.props.location.search.includes("?token")) {
  const email = getQueryVariable(this.props.location.search, "email");
  const token = getQueryVariable(this.props.location.search, "token");
  if (this.state.showValidationModal === false) {
    console.log("Before",this.state.showValidationModal);
    this.setState({
      showValidationModal:true
    })
    // here you get the latest value of showValidationModal state
    this.setState(prevState => console.log(prevState.showValidationModal))

    // here you get the old value.
    console.log("After",this.state.showValidationModal);

  }
}
}