Hello Nick,
I'd start by activating the old project again, that previously worked - just to make sure that the problem is software and not hardware related.
Then do the changes step-by-step, first the controller name, then the RoboTeam etc.
Also, verify that any connected EtherCAT periphery (EK1100 etc.) is correctly powered with the LEDs on.
As you connected the robots via Ethernet, did you make sure that they do not use the same IP address? I don't think that would have an impact on EtherCAT, but who knows...
Finally, a cold-boot from the Shutdown menu, with re-load files ticked, is never a bad idea.
Best,
Johannes