Sorry, I should have been a bit more clear with my instructions. I used the Created by Email dynamic content as an example. What I meant to ask you to try is to use the dynamic content that you are using in your Compose action in place of the Created by Email dynamic content I used in my test.
I'm assuming that whatever dynamic content you've inserted here is what is pulling the user's email address.
Can you confirm if you are using a Person column in your SharePoint list? Or is it a text field.

The Get user profile (V2) action requires the email entered to match the email stored in the User's profile. For example, if you are entering in an email address in all lowercase, but the email address in the User's profile is stored in camel case, it will not return anything.