Long story short. I was look for some undergraduate level research for this July and August, so I contacted a professor like a month ago. Things went very well, and two weeks ago I even had a Skype conversation with one of their PhDs, from which I can tell that they are preparing to include me into their research group, because we talked about a lot of details like everyone's schedule, and they will presumably be my research leader in the future.
At the end of our remote meeting, the PhD told me they will send me a detailed schedule and research topic to me "in one or two weeks", and "feel free to shoot me an email in case I forgot about this". It has been over two weeks since then, so I sent an (extra polite) reminder three days ago, but I still haven't got any response yet.
Is it OK to sent another reminder to them? How long should I wait before doing so?
This is not a duplicate of How to get people to reply to emails and what to make of a no response?, because I am talking about a reminder to a previous reminder that is already sent. Also, the recipient is a PhD instead of a professor.