How long do I need to wait around for the Respondent researcher to show up?

As of now they are 15 minutes late. There's no link to join in or anything, and I asked if there was a link or if they would just call me, so I'm assuming I was meant to get a call. I've been using Respondent for months and this is the first time this has happened.

How long do I need to wait for them to show up? There's no info in the Respondent help center.