They will send the link a couple of hours before the event. Unfortunately, sellers who are not big brokers have their tickets removed from Stubhub 4 hours before the event. So, by the time you get the replacement link, there usually are not many tickets left.
In terms of refund, who knows. Stubhub sold me invalid tickets 50 days ago and I'm still unable to get them to refund the order, or even look into the issue despite calling at least once a week for the past 6 weeks.
My advice is use TickPick next time instead.
Yeah, that's a rough situation. Stubhub used to have incredible customer service. But they were acquired over the last couple years and it is really poor now. The site is great when everything goes smoothly, but it is really difficult and sometimes impossible to resolve issues when they come up. Their customer service team truly does not care about customers.