Regardless Epic Account
Hey there, 4goTTen21!
If you created your Path of Exile account via Epic Games, it will not have an associated email address on our end.
If you would like to add an email address to your Epic Games Path of Exile account so you may use the stand-alone client, you should be able to do so by navigating to the "Manage Connections" page which can be found here.
From there, you can change the email on your account to the email you would like to sign in with on the stand-alone client for Path of Exile.