Whats the difference between Epic and EpicPC?

So if I buy an account that only says Epic as a platform, where do I log into the account?

 

There doesn't seem to be any difference and you can enter both. But I could be wrong

 

I'm asking because I bought an account for the first time yesterday, the platform said "Epic" on it, the problem is that when I want to log in on the PC it doesn't recognize the email and wants to register the email instead of logging in. Unfortunately the saleswoman hasn't answered me since yesterday, she just wanted a video proof that I sent her, since then she's been online all the time but she hasn't helped me.