Is it normal for a potential supervisor to not reply to a student even after they replied before?
Is your deadline for this opportunity within a month or two? If so, a gentle nudge would be appropriate after a week. You could reply to your own email to bring it back to the top of the professor's inbox, saying something at the top like:


  Dear Professor X, I am sure you are very busy, so thank you for your previous response about the PhD position. Please let me know if you would like to further discuss my research experience (details below) or the projects I hope to pursue with you.


If the deadline is extremely close (within the next two weeks?) it might be appropriate to further inquire, "Given that the application deadline is XXX, may I ask whether you are still considering me as a potential student for this PhD position?" (It would be courteous for the professor to tell you if you were out of consideration, but it also might not be necessary to ask for this clarification unless your next action hinges on the response, e.g. asking another faculty member at the institution to sponsor you.)



Edit: Advice on getting replies from busy professors suggests saying that you're "sending a follow-up in case your original message went to spam, or something similar". However, that is less plausible because you previously received a response. (Unless the attachments may have gotten it sent to a spam filter.) I'm not sure whether there is another courteous "little white lie" to deploy here rather than taking the tack of "I am sure you are very busy."