I unlinked both CORE2-ROS from my account and tried to reconfigure them. This does not work.
I let them boot, press the hConf button, connect to the CORE2-ROS, and insert the configuration code (via website and via ssh connection).
Edit: I took the 2 CORE2-ROS home, tried to configure or flash them there. Configuring worked almost instantly at home so I suppose this is a combination of miscommunication/bugginess of the network on my work and the CORE2-ROS.
Somehow I think connecting them to a different network than the one before made them both work/configurable again.