The Trainer is fully functional but there are some bugs with the latest release. Mostly with tethers needing to be cycled like we do with fuel and sometimes they just expire immediately for some reason. Definitely not a high priority but would like it to be more stable eventually.
[Edited by enabels, 12/22/2021 2:30:57 PM]
I would suggest giving it a bit since the game is in Early Access, so it might be a bug in the game
5+ people have the same problem, but it was denied
Just tested it again on the latest trainer and it works fine. Started a shift, oxygen goes down, activated option, oxygen is filled up.