The error "Element not found" means the locator is incorrect. Can you share the HTML source of your test page here?

You'd better add a breakpoint in the line of "self.select_action.click()." and check the HTML source. a typical behavior of a dynamic element is to add some classes to the element. You may try

"//div[contains(@class,'ant-select-selector')])[3]"

to locator the element. If the failure still exists, paste the HTML source of this element here. I will help you to check this issue.