If the buyer has a good track record, chances are s/he is away or unable to respond in a timely fashion - which does happen to us all from time to time. I'd say, allow a couple of days after the weekend, and then reach out again.
It's great that you're asking your fellow domaining peers for advice, but I am curious if you have / had reached out to Flippa Support ([email protected]) yet?
Please do so if you haven't already. If you'd like to ping me the Support Ticket Number once you have reached out, I can make sure you get some resolution on this.