I think mobile use is going out of style; the kids these days are simply operating on telepathy. Hence, it's no longer important to see those desktop/mobile percentages per campaign.
But seriously, yeah, we were moved to the latest version of Constant Contact a couple of weeks ago, and tinkering through it now I can't figure any way to find the splits on individual emails, only the aggregate on the last 50.
Hello @TimL11368 and @mchristo. At this time, the Opens by Device rate only displays for all emails that have been opened over the past 90 days. I can certainly submit feedback for you to our product team to let them know that you would like to be able to view the Opens by Device rate for individual emails. I apologize for any inconvenience this has caused you.