shrine of challenge

Playing on PC no mods are being used. I'm playing a multiplayer game with a few friends and we unlocked the mines hardmode. The only issue is we can't change it back to normal mode; Going to the shrine of challenge give us the text that it was "sealed" and that the mines will be normal the next...

Regardless of changing the shrine to more powerful monsters or weaker monsters, and waiting the next day for it to change to the normal mines, my girlfriend and I cannot get the normal mines. We have tried changing it back and for between the difficulties multiple times. We are permanently set...