How frustrating! I would recommend using minecraft in the classroom instead of relying on vox-l. For a few months now, there has been a bug in vox-l where it's not possible to see creatures in it or lightning. The Development team currently doesn't have the time, manpower and resources to fix it (it requires a lot of people working together to fix this kind of bug). When completing the vox-l skills and drills badges, they should automatically unlock after you get the correct answer, without you needing to test them in the simulator -- please let me know if that's not the case.
Even in the standalone you wouldn't be able to see creatures due to the bug.
The older skills and drills badges, using the old simulator must be tested in minecraft, because that old form of the simulator uses outdated plugins that no longer work in most browsers. (There's a skip simulator button at the bottom of the badge instructions on those badges)
The redirect error is happening because a month ago or so, Development dealt with a bug on the login website not redirecting like it should. This is probably related and I'll let them know about it right now. Usually the way for users now to fix this kind of problem on their end is to type into the url field https:// mod.learntomod.com but I realize the app doesn't have a urll field. We're very sorry about the inconvenience.
Are you have any issues running badge mods in minecraft? I can help you with that.