MyRogers app is accessible when I'm on my data, there is no problem at all, it's only when I try to log on using WiFi. You could be right regarding data not being charged, I do not know. I'm not with Rogers & if I use MyRogers app to check the usage ...
Are you using your Data to log in or WiFi? I can log into MyRogers app, wth my email as my username & password, but, can't log in when I'm on WiFi. I don't remember changing any settings on my Rogers Coda router or Eero.