CR notification not bring sent

Dear all,

The plugin is good and I have been using them for quote a few month and everything looks good.

Today I was asking a customer to write something about the item he purchased. He told he never received any email via CR. I was looking into the setting and changed it to manual sending, and sent it again to him. Still, he did not receive anything.

So I tried to fix it: I updated woocommerce and the plugin to the latest version. And I tested it in the last row of setting: Send Test. The result is: “Error: email could not be sent, please check if your settings are correct and saved.”

It is very strange and please help me. THanks.