Wooocommce Shipping Plugin, how to get error message to show around the shipping calculator?

Question

UPDATE: I've solved it by storing the messages I want to show in the cookie (WC()->session).

And querying that in the method outside of the class.

However, I'd still like to understand why add_action("hook", [$this, "method"]) didn't work inside of the class.

I'm working on a Shipping plugin and would like to show error messages during calcuate_shipping()

I've tried to add_action to various hook like "woocommerce_after_shipping_calculator" or "woocommerce_after_cart" or "woocommerce_after_shipping_calculator"

with:

add_action("woocommerce_after_shipping_calculator", [$this, show_error()])

inside the calculate_shipping

I can echo some text if I defined the add_action outside my plugin class and use a normal method, but then I'm not sure how I could grab that error msg without using update_option, for that particular time the user requested.

I know I can use wc_notice(msg, 'error') but that message is above the cart box and can be out of screen if the user is focused around the calculator.

From what I understand, woocommerce_after_shipping_calculator hook should come after calculate_shipping is called on my plugin, so it should display something?

Many thanks in advance