Move on. No big deal.
You run any leagues? I've never had this much trouble getting people to be active participants in any league... Even one with people who don't personally know one another, like this one.
I had reservations restarting the league again this season because of the same issues last season. I hear what you're saying and I'll give them their allotted time but not not one second more (well, at least not past Thursday the 16th cause I'll be sleeping when the Aug 15th deadline hits at midnight).