If SeriousMD does not load on your web browser, it's most likely due to the browser being outdated. Typically happens on older computers and Android devices. Please update the software and it will work. We have to require this for the security and privacy of your data.
If you are on iOS 9.0 or lower, your Safari browser is already outdated and you should instead download the SeriousMD app to login. You might also want to update your iOS firmware to the latest one.